ST2.2

EDI
Combined session: global magnetospheric dynamics and dayside magnetosphere interaction

The first part of the combined session is dedicated to the global magnetospheric dynamics. The state of the magnetosphere is controlled mainly by solar wind conditions. The interplanetary magnetic field (IMF) as well as solar wind plasma parameters regulate the energy input into the magnetosphere. While the IMF’s direction plays an important role in the coupling between the solar wind and magnetosphere, the questions remain on the effectiveness of the different plasma penetration mechanisms, their distribution at the magnetopause, and consequent global magnetospheric dynamics. Furthermore, the solar wind plasma parameters, such as density and velocity, may also change the magnetospheric state, but links between types of the solar wind structures and different magnetospheric modes need further investigation. The other open questions on the global magnetospheric dynamics include how the pre-conditioning of the magnetosphere changes its response to the solar wind impact and what are the roles of the ionosphere and ionosphere-magnetosphere coupling in the transition between magnetospheric modes. Global magnetospheric dynamics can be studied employing numerical simulations (MHD or kinetic), using empirical and semi-empirical models, and with the help of multipoint spacecraft observations. Besides, some past and future space missions can make global magnetospheric imaging providing information about positions and dynamics of the magnetospheric boundaries and global distribution of the ionospheric currents. We welcome any work presenting results on the global dynamics of the Earth’s magnetosphere as well as other planets’ magnetospheres.


The second part of the combined sessions is dedicated to the question how the Earth’s magnetosphere is affected by transient solar wind features. During the interaction between the solar wind transients and the Geospace system, important energy transfer and transport occur. Solar energy in various forms can propagate into the magnetosphere and ionosphere. In the meanwhile, charged particle energy can be transformed to electromagnetic energy, and vice versa. In-depth understanding of how the magnetosphere responds to transient solar wind features will enhance our knowledge on the solar wind-magnetosphere-ionosphere coupling. This special session will address the processes by which solar wind mass, momentum, and energy enter the magnetosphere. Regions of interest include the foreshock, bow shock, magnetosheath, magnetopause, cusps, the dayside magnetosphere, and the dayside ionosphere. This special session will provide a forum for the latest results from in-situ spacecraft observations, ground-based observations, and global simulations. Coordinated multi-point observations are especially encouraged. Planetary dayside Magnetospheric Interaction studies are also welcome.

Convener: C.-Philippe Escoubet | Co-conveners: Andrey Samsonov, Quanqi Shi, Yulia Bogdanova, Jie RenECSECS, David Sibeck, Hui Zhang, Qiugang Zong
vPICO presentations
| Tue, 27 Apr, 11:00–17:00 (CEST)

vPICO presentations: Tue, 27 Apr

Chairpersons: Quanqi Shi, C.-Philippe Escoubet, Hui Zhang
Dayside magnetosphere interaction
11:00–11:05
11:05–11:15
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EGU21-8571
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ECS
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solicited
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Highlight
Terry Zixu Liu, Xin An, Hui Zhang, and Drew Turner

Foreshock transients are ion kinetic structures in the ion foreshock. Due to their dynamic pressure perturbations, they can disturb the bow shock, magnetosheath, magnetopause, and magnetosphere-ionosphere system. Recent studies found that they can also accelerate particles through shock drift acceleration, Fermi acceleration, betatron acceleration, and magnetic reconnection. Although foreshock transients are important, how they form is still not fully understood. Using particle-in-cell simulations and MMS observations, we propose a physical formation process that the positive feedback of demagnetized foreshock ions on the varying magnetic field caused by the foreshock ion Hall current enables an “instability” and the growth of the structure.      

How to cite: Liu, T. Z., An, X., Zhang, H., and Turner, D.: A kinetic formation model of foreshock transients, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8571, https://doi.org/10.5194/egusphere-egu21-8571, 2021.

11:15–11:17
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EGU21-1954
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Highlight
Hui Zhang

Hot flow anomalies (HFAs), which are frequently observed near the Earth’s bow shock, are phenomena resulting from the interaction between interplanetary discontinuities and the Earth’s bow shock. Such transient phenomena upstream of the bow shock can cause significant deformation of the bow shock and the magnetopause, generating traveling convection vortices, field-aligned currents, and ULF waves in the Earth’s magnetosphere. A large HFA lasting about 16 minutes was observed by MMS on November 19, 2015. In this study, energetic particle sounding method with high time resolution (150 ms) Fast Plasma Investigation (FPI) data is used to determine the deformed magnetopause distances, orientations, and structures during the interval when MMS crossed the deformed magnetopause. The estimated radius of curvature of the deformed magnetopause is 2.2 RE.

How to cite: Zhang, H.: Energetic Particle Sounding of the Magnetopause Deformed by a Hot Flow Anomaly: MMS Observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1954, https://doi.org/10.5194/egusphere-egu21-1954, 2021.

11:17–11:19
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EGU21-3424
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ECS
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Highlight
Wei-Jie Sun, James Slavin, Rumi Nakamura, Daniel Heyner, and Johannes Mieth

BepiColombo is a joint mission of the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) to the planet Mercury. The BepiColombo mission consists of two spacecraft, which are the Mercury Planetary Orbiter (MPO) and Mercury Magnetospheric Orbiter (Mio). The mission made its first planetary flyby, which is the only Earth flyby, on 10 April 2020, during which several instruments collected measurements. In this study, we analyze MPO magnetometer (MAG) observations of Flux Transfer Events (FTEs) in the magnetosheath and the structure of the subsolar magnetopause near the  flow stagnation point. The magnetosheath plasma beta was high with a value of ~ 8 and the interplanetary magnetic field (IMF) was southward with a clock angle that decreased from ~ 100 degrees to ~ 150 degrees.  As the draped IMF became increasingly southward several of the flux transfer event (FTE)-type flux ropes were observed. These FTEs traveled southward indicating that the magnetopause X-line was located northward of the spacecraft, which is consistent with a dawnward tilt of the IMF. Most of the FTE-type flux ropes were in ion-scale, <10 s duration, suggesting that they were newly formed. Only one large-scale FTE-type flux rope, ~ 20 s, was observed. It was made up of two successive bipolar signatures in the normal magnetic field component, which is evidence of coalescence at a secondary reconnection site. Further analysis demonstrated that the dimensionless reconnection rate of the re-reconnection associated with the coalescence site was ~ 0.14. While this investigation was limited to the MPO MAG observations, it strongly supports a key feature of dayside reconnection discovered in the Magnetospheric Multiscale mission, the growth of FTE-type flux ropes through coalescence at secondary reconnection sites.

How to cite: Sun, W.-J., Slavin, J., Nakamura, R., Heyner, D., and Mieth, J.: Dayside Magnetopause Reconnection and Flux Transfer Events: BepiColombo Earth-Flyby, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3424, https://doi.org/10.5194/egusphere-egu21-3424, 2021.

11:19–11:21
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EGU21-4490
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Highlight
C.-Philippe Escoubet and the Cluster-MMS team

Magnetosheath High Speed Jets (HSJs) are regularly observed downstream of the Earth’s bow shock. Determining their origin from spacecraft observations is however a challenge since (1) L1 solar wind monitors are usually used with their inherent inaccuracy when plasma and magnetic data are propagated to the bow shock, (2) the number of measurement points around the bow shock are always limited. Various mechanisms have been proposed to explain HSJs such as bow shock ripples, solar wind discontinuities, foreshock transients, pressure pulses or nano dust clouds and it is difficult to relate these to HSJs with the lack of simultaneous measurements near the bow shock and immediately upstream.  We will use a special Cluster campaign, where one spacecraft was lagged 8 hours behind the three other spacecraft, to obtain near-Earth solar wind measurements upstream of the bow shock, together with simultaneous measurements in the magnetosheath. The event of interest is first observed by ACE on 13 January 2019 as a short 10 minutes period of IMF-Bx dominant (cone angle around 140 deg.). This IMF-Bx dominant period is also observed, one hour later, by THEMIS B and C (ARTEMIS) and Geotail, which were at 60 and 25 RE from Earth on the dawnside. Cluster 1 and Cluster 2 just upstream of the bow shock, at 17 RE from Earth, observed also such IMF-Bx dominant period together with energetic ions reflected from the bow shock and foreshock transients. Preliminary analysis indicate that these transients would be hot flow anomalies. Finally, Cluster 3 and 4 and MMS1-4, a few RE from each other downstream of the shock, observed a turbulent magnetosheath with HSJs for 15 minutes. The HSJ characteristics are investigated with the constellation of 6 spacecraft, as well as their relation to hot flows anomalies observed upstream.

How to cite: Escoubet, C.-P. and the Cluster-MMS team: Magnetosheath high speed jets and foreshock transients observed by Cluster and MMS, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4490, https://doi.org/10.5194/egusphere-egu21-4490, 2021.

11:21–11:23
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EGU21-7921
Minna Palmroth, Savvas Raptis, Tomas Karlsson, Jonas Suni, Lucile Turc, Andreas Johlander, Urs Ganse, Yann Pfau-Kempf, Xochitl Blanco-Cano, Mojtaba Akhavan-Tafti, Markus Battarbee, Maxime Grandin, Maxime Dubart, Vertti Tarvus, and Adnane Osmane

Magnetosheath jets are regions of high dynamic pressure, which can traverse from the bow shock towards the magnetopause. Recent modelling efforts, limited to a single jet and a single set of upstream conditions, have provided the first estimations about how the jet parameters behave as a function of position within the magnetosheath. Here we expand the earlier results by making the first statistical investigation of the jet dimensions and parameters as a function of their lifetime within the magnetosheath. To verify the simulation behaviour, we first identify jets from Magnetosphere Multi-Scale (MMS) spacecraft data (6142 in total) and confirm the Vlasiator jet general behaviour using statistics of 924 simulated individual jets. We find that the jets in the simulation are in excellent quantitative agreement with the observations, confirming earlier findings related to jets using Vlasiator. The jet density, dynamic pressure and magnetic field intensity show a sharp jump at the bow shock, which decreases towards the magnetopause. The jets appear  compressive and cooler than the magnetosheath at the bow shock, while during their propagation towards the magnetopause they thermalise. Further, the shape of the jets flatten as they progress through the magnetosheath. They are able to maintain their flow velocity and direction within the magnetosheath flow pattern, and they end up preferentially to the side of the magnetosheath behind the quasi-parallel shock. Finally, we find that Vlasiator jets during low solar wind Alfvén Mach number (MA) are shorter in duration, smaller in their extent, and weaker in terms of dynamic pressure and magnetic field intensity as compared to the jets during high MA. 

How to cite: Palmroth, M., Raptis, S., Karlsson, T., Suni, J., Turc, L., Johlander, A., Ganse, U., Pfau-Kempf, Y., Blanco-Cano, X., Akhavan-Tafti, M., Battarbee, M., Grandin, M., Dubart, M., Tarvus, V., and Osmane, A.: Magnetosheath jet evolution as a function of lifetime: Global hybrid-Vlasov simulations compared to MMS observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7921, https://doi.org/10.5194/egusphere-egu21-7921, 2021.

11:23–11:25
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EGU21-11325
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ECS
Jonas Suni, Minna Palmroth, Lucile Turc, Markus Battarbee, Andreas Johlander, Vertti Tarvus, Markku Alho, Maxime Dubart, Urs Ganse, Maxime Grandin, Konstantinos Papadakis, and Yann Pfau-Kempf

Magnetosheath jets are a class of phenomena usually defined as pulses of high dynamic pressure in the magnetosheath, but the details of their origins are currently unclear. Many theories on the origin of magnetosheath jets have been developed, such as bow shock rippling and foreshock structures. The usefulness of spacecraft data in studying some of them is limited, due to the transient and localised nature of jets. We use the 5D global hybrid-Vlasov simulation Vlasiator in a statistical study to investigate the relationship between compressive structures in the foreshock and magnetosheath jets. Foreshock compressive structures and magnetosheath jets are identified and their evolution over time is tracked. We find that up to 75% of magnetosheath jets forming at the bow shock are associated with foreshock compressive structures impacting the bow shock at the same location. Furthermore, magnetosheath jets that are associated with foreshock compressive structures penetrate deeper into the magnetosheath than jets that are not associated with foreshock compressive structures.

How to cite: Suni, J., Palmroth, M., Turc, L., Battarbee, M., Johlander, A., Tarvus, V., Alho, M., Dubart, M., Ganse, U., Grandin, M., Papadakis, K., and Pfau-Kempf, Y.: Foreshock compressive structure-magnetosheath jet coupling in a global hybrid-Vlasov simulation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11325, https://doi.org/10.5194/egusphere-egu21-11325, 2021.

11:25–11:27
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EGU21-5635
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ECS
Vertti Tarvus, Lucile Turc, Markus Battarbee, Jonas Suni, Xóchitl Blanco-Cano, Urs Ganse, Yann Pfau-Kempf, Markku Alho, Maxime Dubart, Maxime Grandin, Andreas Johlander, Konstantinos Papadakis, and Minna Palmroth

Foreshock cavitons are transient structures forming in Earth's foreshock as a result of non-linear interaction of ultra-low frequency waves. Cavitons are characterised by simultaneous density and magnetic field depressions with sizes of the order of 1 Earth radius. These transients are advected by the solar wind towards the bow shock, where they may accumulate shock-reflected suprathermal ions and become spontaneous hot flow anomalies (SHFAs), which are characterised by an enhanced temperature and a perturbed bulk flow inside them.
    Both spacecraft measurements and hybrid simulations have shown that while cavitons and SHFAs are carried towards the bow shock by the solar wind, their motion in the solar wind rest frame is directed upstream. In this work, we have made a statistical analysis of the propagation properties of cavitons and SHFAs using Vlasiator, a hybrid-Vlasov simulation model. In agreement with previous studies, we find the transients propagating upstream in the solar wind rest frame. Our results show that the solar wind rest frame motion of cavitons is aligned with the direction of the interplanetary magnetic field, while the motion of SHFAs deviates from this direction. We find that SHFAs have a faster solar wind rest frame propagation speed than cavitons, which is due to an increase in the sound speed near the bow shock, affecting the speed of the waves in the foreshock.

How to cite: Tarvus, V., Turc, L., Battarbee, M., Suni, J., Blanco-Cano, X., Ganse, U., Pfau-Kempf, Y., Alho, M., Dubart, M., Grandin, M., Johlander, A., Papadakis, K., and Palmroth, M.: Propagation properties of foreshock cavitons and spontaneous hot flow anomalies: Statistical results from a global hybrid-Vlasov simulation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5635, https://doi.org/10.5194/egusphere-egu21-5635, 2021.

11:27–11:29
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EGU21-14535
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ECS
Xiaoqiong Zhu, Mengmeng Wang, Quanqi Shi, Hui Zhang, Anmin Tian, Shutao Yao, Ruilong Guo, Ji Liu, Shichen Bai, Shuai Zhang, Wensai Shang, and Zhe Niu

Hot flow anomalies (HFAs), characterized by heated plasma and flow deflection, are frequently observed near Earth’s and other planetary bow shocks. There are two kinds of HFAs, classic HFAs formed by the interaction of tangential discontinuities (TD) and the bow shock, and spontaneous HFAs (SHFAs) which are not associated with discontinuties. A statistical study of the propagation characteristics of HFA edges has been performed base on 19 classic HFAs and 23 SHFAs with one-dimensional edges observed by Cluster from 2001 to 2010. The propagation velocity and normal direction of each edge are calculated using the timing method, the minimum directional difference (MDD) method, and the spatial-temporal difference (STD) method. The angle between the leading edge normal and the corresponding TD normal is less than 30 degrees for 93% of the classic HFAs. The angle between the edge normal and background magnetic field is near 90 degrees for 74% of the SHFAs. Observations indicate that the leading edge of the classic HFAs propagates along the same direction as the driving TD and the SHFAs propagate perpendicular to the background magnetic field. Furthermore, we find that all 42 HFAs propagate toward the Earth in the spacecraft frame as expected. However, in the solar wind frame HFAs have different propagation directions (i.e., toward the Earth, the Sun or be stationary in the solar wind frame).

How to cite: Zhu, X., Wang, M., Shi, Q., Zhang, H., Tian, A., Yao, S., Guo, R., Liu, J., Bai, S., Zhang, S., Shang, W., and Niu, Z.: Propagation characteristics of hot flow anomalies, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14535, https://doi.org/10.5194/egusphere-egu21-14535, 2021.

11:29–11:31
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EGU21-6971
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ECS
Kun Zhang, Seth Dorfman, Urs Ganse, Lucile Turc, and Chen Shi

Energetic ions reflected and accelerated by the Earth’s bow shock travel back into the solar wind, forming the ion foreshock, and generate ultralow frequency (ULF) waves. Such ULF waves have been extensively studied over the past few decades using satellite measurements. However, the spatial variations of the wave properties cannot be well resolved by satellite observations due to the limited number of available spacecraft simultaneously inside the ion foreshock. Therefore, we conduct a global survey of the ULF wave properties in the ion foreshock through analysis of a Vlasiator (a hybrid-Vlasov code) simulation. Previous studies validated that this simulation well reproduced Earth’s foreshock and the ULF waves in it [e.g., Palmroth et al., 2015; Turc et al., 2018]. Here we focus on the wave properties, including frequency, ellipticity, polarization, wave normal angle and growth rate, of the well-known 30-sec wave and its multiple harmonics. We report that the ULF waves near the edge of the foreshock are very different from the waves in the center of the foreshock. We also show the related ion distribution and discuss the connection between the observed ion beams and ULF waves, aiming at understanding the cause of the observed differences in wave properties.

 

This study is supported by NASA grant 80NSSC20K0801. Vlasiator is developed by the European Research Council Starting grant 200141-QuESpace, and Consolidator grant GA682068-PRESTISSIMO received by the Vlasiator PI. Vlasiator has also received funding from the Academy of Finland. See www.helsinki.fi/vlasiator

 

Palmroth, M., et al. (2015), ULF foreshock under radial IMF: THEMIS observations and global kinetic simulation Vlasiator results compared, J. Geophys. Res. Space Physics, 120, 8782–8798, doi:10.1002/2015JA021526.

Turc, L., Ganse, U., Pfau-Kempf, Y., Hoilijoki, S., Battarbee, M., Juusola, L., et al. (2018). Foreshock properties at typical and enhanced interplanetary magnetic field strengths: results from hybrid-Vlasov simulations. Journal of Geophysical Research: Space Physics, 123, 5476–5493. doi:10.1029/2018JA025466.

How to cite: Zhang, K., Dorfman, S., Ganse, U., Turc, L., and Shi, C.: Global structure and properties of ULF waves in the ion foreshock observed in a Hybrid-Vlasov simulation., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6971, https://doi.org/10.5194/egusphere-egu21-6971, 2021.

11:31–11:33
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EGU21-3433
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ECS
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Highlight
Xingran Chen, Qiugang Zong, Ying Liu, Yixin Hao, Suiyan Fu, Jie Ren, and Chao Yue

We employ conjunctive observations of particle fluxes and electromagnetic fields in the solar wind, magnetosheath, and dayside magnetosphere to investigate the radiation belt dynamics in response to the impingement of a fast forward interplanetary shock on 7 September 2017. Particularly, drift echoes associated with the one-kick acceleration caused by the shock-induced magnetosonic pulse and oscillations in the Pc 4 range associated with the azimuthally localized ULF waves are identified concurrently in the in-situ particle measurements obtained by the twin Van Allen Probes in the dayside outer radiation belt. Based on this observational evidence, we demonstrate that the radiation bet can be efficiently disturbed via the two mechanisms simultaneously by the shock arrival. We also depict the characteristic features to distinguish between the two mechanisms from an observational approach.

How to cite: Chen, X., Zong, Q., Liu, Y., Hao, Y., Fu, S., Ren, J., and Yue, C.: Shock-induced radiation belt dynamics: Coordinated observations of drift echoes and ULF modulations in the dayside magnetosphere , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3433, https://doi.org/10.5194/egusphere-egu21-3433, 2021.

11:33–11:35
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EGU21-14176
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ECS
Zhe Niu, Alexander Degeling, and Quanqi Shi

For the study of Earth's radiation belts, an outstanding problem is the identification and prediction of dynamic variations of Earth's trapped energetic particles, in particular during geomagnetic storms. Statistical studies indicate that different types of geomagnetic storms (e.g. CIR and CME driven storms) have differing efficiencies in their ability to cause energization, transport and loss of energetic particles. This is most likely due to differences in the dominant mechanisms by which particles are affected between the storm types, and the locations within the magnetosphere where these mechanisms operate. For example, the dominant external generation mechanism for Pc5 ULF waves during CME driven storms may be magnetopause buffeting across the dayside, while for CIR driven storms the Kelvin-Helmholtz Instability (KHI) along the morning and evening flanks is more likely dominant. This changes the location and efficiency by which ULF waves can resonantly interact with radiation belt particles in these two storm types.

In this study, we use a 2D MHD wave model to investigate how the dominant generation mechanism in the case of CIR and CME driven storms determines the ability for externally generated wave power to penetrate deeply into the magnetosphere. In order to do this, we model ideal MHD waves in a 2D box model magnetosphere with a parabolic magnetopause boundary layer. We consider how fluctuations in dynamic pressure generate magnetopause buffeting perturbations that launch MHD fast mode waves, following the approach of Degeling et al., JGR 2011. We also include in our simulation a simple model for magnetosheath flow, and calculate the local linear KHI growth rate for perturbations along the magnetopause flanks as a function of frequency to provide a KHI driven wave source.

How to cite: Niu, Z., Degeling, A., and Shi, Q.: Comparison of External ULF wave Sources in Driving Radiation Belt Electron Dynamics, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14176, https://doi.org/10.5194/egusphere-egu21-14176, 2021.

11:35–11:37
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EGU21-14090
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ECS
Xiao Ma, Anmin Tian, Quanqi Shi, Shichen Bai, Ji Liu, Ruilong Guo, and Shutao Yao

In the two flanks of the Earth’s magnetosphere, the compressional Pc5 waves are often observed. Previous study suggests that these waves are usually excited by plasma pressure anisotropy such as drift mirror instability. Interestingly, whistler mode waves are often observed in the magnetic trough regions of the compressional Pc5 waves. In this study, we use 10 years (2007-2016) THEMIS A data to study the electron distributions in the compressional Pc5 waves associated with the whistler mode waves. We find three typical electron pitch angle distributions (PADs) in these compressional waves: cigar-shape, donut-shape and pancake-shape. They predominantly occur at tens to hundreds eV, several keV and >10 keV, respectively. The interaction effects between the electrons and whistler waves inside the magnetic troughs are stressed in understanding the formation of these PADs.

How to cite: Ma, X., Tian, A., Shi, Q., Bai, S., Liu, J., Guo, R., and Yao, S.: Electron Pitch Angle Distributions in the Compressional Pc5 Waves, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14090, https://doi.org/10.5194/egusphere-egu21-14090, 2021.

11:37–11:39
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EGU21-8603
Anmin Tian

Pc5 compressional waves are frequently observed in the outer magnetosphere with mirror mode features. Due to the limited spatial coverage of spacecraft, their overall structure is still poorly understood. In this work, the wave structure and motion characteristics are statistically investigated based on the MMS data from September to October 2015. During this time period, the apogees of the MMS spacecraft were located in the outer dusk magnetosphere, and the spacecraft has regular tetrahedral configuration that facilitates the application of multi-spacecraft analysis techniques. The magnetic trough boundaries are identified, and their normal direction, current density and velocity of these boundaries are calculated. We found that the magnetic trough has a magnetic bottle topology along the field line. In the r-a plane, the two boundaries has an open angle toward the radial direction.The boundaries mainly move sunward in the GSE XY plane with average speed of ~26km/s. The poloidal Alfven mode is found to be coupling with the compressional mode oscillation. It suggests that our observations could be explained by the theory of drift Alfven ballooning mirror instability.

How to cite: Tian, A.: Study of Pc5 compressional waves by MMS observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8603, https://doi.org/10.5194/egusphere-egu21-8603, 2021.

11:39–11:41
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EGU21-2884
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ECS
Anna Salohub, Jana Šafránková, and Zdeněk Němeček

The foreshock is a region filled with a turbulent plasma located upstream the Earth’s bow shock where interplanetary magnetic field (IMF) lines are connected to the bow shock surface. In this region, ultra-low frequency (ULF) waves are generated due to the interaction of the solar wind plasma with particles reflected from the bow shock back into the solar wind. It is assumed that excited waves grow and they are convected through the solar wind/foreshock, thus the inner spacecraft (close to the bow shock) would observe larger wave amplitudes than the outer (far from the bow shock) spacecraft. The paper presents a statistical analysis of excited ULF fluctuations observed simultaneously by two closely separated THEMIS spacecraft orbiting the Moon under a nearly radial IMF. We found that ULF fluctuations (in the plasma rest frame) can be characterized as a mixture of transverse and compressional modes with different properties at both locations. We discuss the growth and/or damping of ULF waves during their propagation.

How to cite: Salohub, A., Šafránková, J., and Němeček, Z.: Foreshock ULF fluctuations near the Moon: THEMIS observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2884, https://doi.org/10.5194/egusphere-egu21-2884, 2021.

11:41–11:43
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EGU21-7255
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ECS
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Highlight
Lucile Turc, Markus Battarbee, Urs Ganse, Andreas Johlander, Yann Pfau-Kempf, Vertti Tarvus, Hongyang Zhou, Markku Alho, Maxime Dubart, Maxime Grandin, Kostis Papadakis, Jonas Suni, and MInna Palmroth

The foreshock, extending upstream of the quasi-parallel shock and populated with shock-reflected particles, is home to intense wave activity in the ultra-low frequency range. The most commonly observed of these waves are the “30 s” waves, fast magnetosonic waves propagating sunward in the plasma rest frame, but carried earthward by the faster solar wind flow. These waves are thought to be the main source of Pc3 magnetic pulsations (10 – 45 s) in the dayside magnetosphere. A handful of case studies with suitable spacecraft conjunctions have allowed simultaneous investigations of the wave properties in different geophysical regions, but the global picture of the wave transmission from the foreshock through the magnetosheath into the magnetosphere is still not known. In this work, we use global simulations performed with the hybrid-Vlasov model Vlasiator to study the Pc3 wave properties in the foreshock, magnetosheath and magnetosphere for different solar wind conditions. We find that in all three regions the wave power peaks at higher frequencies when the interplanetary magnetic field strength is larger, consistent with previous studies. While the transverse wave power decreases with decreasing Alfvén Mach number in the foreshock, the compressional wave power shows little variation. In contrast, in the magnetosheath and the magnetosphere, the compressional wave power decreases with decreasing Mach number. Inside the magnetosphere, the distribution of wave power varies with the IMF cone angle. We discuss the implications of these results for the propagation of foreshock waves across the different geophysical regions, and in particular their transmission through the bow shock.

How to cite: Turc, L., Battarbee, M., Ganse, U., Johlander, A., Pfau-Kempf, Y., Tarvus, V., Zhou, H., Alho, M., Dubart, M., Grandin, M., Papadakis, K., Suni, J., and Palmroth, M.: Foreshock wave transmission into the magnetosheath and magnetosphere: results from global hybrid-Vlasov simulations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7255, https://doi.org/10.5194/egusphere-egu21-7255, 2021.

11:43–11:45
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EGU21-3643
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Highlight
Jean Berchem, Giovanni Lapenta, Robert L. Richard, Philippe Escoubet, and Simon Wing

An important step in comprehending the effects of solar wind structures on the magnetosphere is to develop an understanding of their impact on the dayside magnetopause.  While most of the time global magnetohydrodynamic (MHD) models describe adequately the large-scale effects of solar wind structures on the magnetopause, recent spacecraft observations in the near Earth solar wind indicate that solar wind discontinuities have plasma features that are often not accurately described by MHD.  In this presentation, we report our progress in gaining a comprehensive understanding of kinetic processes occurring at the magnetopause as solar wind structures impact the dayside magnetosphere. Our approach combines implicit PIC simulations with global MHD simulations of the solar wind-magnetosphere-ionosphere system. The global simulation sets the overall configuration of the magnetosphere, while fields and plasma moments of a sub-domain of the global simulation are used to set initial and boundary conditions of the PIC code. Results are discussed in the context of spacecraft observations.

How to cite: Berchem, J., Lapenta, G., Richard, R. L., Escoubet, P., and Wing, S.: Kinetic Modeling of the Impact of Solar Wind Discontinuities on the Magnetopause, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3643, https://doi.org/10.5194/egusphere-egu21-3643, 2021.

11:45–11:47
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EGU21-862
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ECS
Kevin Alexander Blasl, Rumi Nakamura, Takuma Nakamura, and Ferdinand Plaschke

The Kelvin-Helmholtz instability (KHI) is one of the main drivers of plasma transport across Earth’s magnetopause. Statistical studies have shown that it occurs much more frequently during periods of northward interplanetary magnetic field (IMF). Here we present MMS observations of the instability during southward IMF on September 23, 2017.

Two MMS intervals featuring plasma parameters fulfilling the instability criterion for KH waves are studied. A boundary normal vector analysis indicates the presence of linear waves and a magnetosheath side crossing of a vortex in these intervals. Correspondingly, clear signatures of Low Density Faster Than Sheath (LDFTS) plasma, in general located at the magnetosheath side of vortices, are found indicating a rolled-up vortex structure. Specific variations of the ion bulk velocity and the total pressure strengthen the argument for the detection of linear waves. Interestingly, the vortex-like event features a constant total pressure, which is explained by a magnetosheath side crossing of a vortex structure.

The MMS observations are compared to simulation results from 2D and 3D fully kinetic PIC simulations performed using the plasma parameters observed around the two MMS events. A linearity analysis of the fastest growing mode of the 2D simulation results suggests the detection of the vortex-like event in the early nonlinear phase.

The simulation further demonstrates that the secondary instabilities such as the lower-hybrid drift instability (LHDI) and the Rayleigh-Taylor instability (RTI) grow near the edge of the non-linearly developed KH vortex and strongly disturb the vortex structure. The elongated vortex arm due to the RTI together with disturbances of the vortex structure can also lead to the observed constant total pressure in MMS data. Given the above quantitative consistencies of the simulation and the MMS observations in the earlier growth phase of the KHI, these results suggest that the secondary modes may reduce the observation probability of KH wave/vortex structures during southward IMF.

How to cite: Blasl, K. A., Nakamura, R., Nakamura, T., and Plaschke, F.: MMS observations of the KHI during southward IMF and comparison to 2D and 3D simulations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-862, https://doi.org/10.5194/egusphere-egu21-862, 2021.

11:47–11:49
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EGU21-13992
Wensai Shang, Binbin Tang, Quanqi Shi, and Et al

The Earth's magnetopause is highly variable in location and shape and is modulated by solar wind conditions. On 8 March 2012, the ARTEMIS probes were located near the tail current sheet when an interplanetary shock arrived under northward interplanetary magnetic field conditions and recorded an abrupt tail compression at ∼(-60, 0, -5) Re in Geocentric Solar Ecliptic coordinate in the deep magnetotail. ~ 10 minutes later, the probes crossed the magnetopause many times within an hour after the oblique interplanetary shock passed by. The solar wind velocity vector downstream from the shock was not directed along the Sun-Earth line but had a significant Y component. We propose that the compressed tail was pushed aside by the appreciable solar wind flow in the Y direction. Using a virtual spacecraft in a global magnetohydrodynamic (MHD) simulation, we reproduce the sequence of magnetopause crossings in the X-Y plane observed by ARTEMIS under oblique shock conditions, demonstrating that the compressed magnetopause is sharply deflected at lunar distances in response to the shock and solar wind Vy effects. The results from two global MHD simulations show that the shocked magnetotail at lunar distances is mainly controlled by the solar wind direction with a timescale of about a quarter hour, which appears to be consistent with the windsock effect. The results also provide some references for investigating interactions between the solar wind/magnetosheath and lunar nearside surface during full moon time intervals, which should not happen in general.

How to cite: Shang, W., Tang, B., Shi, Q., and al, E.: Unusual Location of the Geotail Magnetopause Near Lunar Orbit: A Case Study, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13992, https://doi.org/10.5194/egusphere-egu21-13992, 2021.

11:49–11:51
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EGU21-10648
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ECS
Emanuele Cazzola, Dominique Fontaine, and Philippe Savoini

This work will be giving new insights into the global Quasi-Perpendicular interaction effects of the Solar Wind with a realistic three-dimensional terrestrial-like curved Bow Shock (BS) by means of hybrid computer simulations.
The Bow-Shock profoundly changes its behavior for different incoming Solar Wind conditions. For Alfvénic Mach numbers greater than a specific threshold, the Bow-Shock shows an intense rippling phenomenon propagating along its surface, as well as the formation of a set of waves in the near-Earth flanks.
A similar rippling has been observed from different independent in-situ satellite crossings, as well as studied with ad-hoc computer simulations configured with 2D-planar shocks, conclusively confirming the highly kinetic nature of this phenomenon. Yet, the possible effects of a global three-dimensional curved interaction are still poorly described.
As such, we have performed a series of 3D simulations at different Alfvénic Mach numbers, different plasma beta - ratio between the thermal to the magnetic pressures - and different incoming Interplanetary Magnetic Field (IMF) configurations with the hybrid code LatHyS, which was already successfully used for similar past analyses.
Particularly, we have found that the ripples follow a pattern not directly driven by the IMF direction as initially expected, but rather a Nose-to-Flanks propagation with the rippling onset region  being significantly displaced from the nose position. Additionally, this phenomenon seems to be mainly confined to the plane on where the IMF direction lies, with the perpendicular cross-sections showing only a slight oscillation.
Finally, we have observes a significant ions acceleration in the local perpendicular directions along the flanks modulations, which is most likely related to the local IMF-BS normal fluctuations occurring in the ripples boundary.

How to cite: Cazzola, E., Fontaine, D., and Savoini, P.: On the Bow-Shock dynamics in response to a Quasi-Perpendicular interaction with different Solar Wind conditions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10648, https://doi.org/10.5194/egusphere-egu21-10648, 2021.

11:51–11:53
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EGU21-15357
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ECS
Yuchen Xiao, Shutao Yao, Ruilong Guo, Quanqi Shi, Anmin Tian, Shichen Bai, and Ji Liu

Flux ropes have attracted extensive attention due to their importance in studying instantaneous magnetic reconnection over the past years. Recently, with the improvement of high spatio-temporal resolution measurements, kinetic-scale flux ropes have been detected. However, their generation and energy energization are still unclear. In this study, electron-scale filamentary currents within two adjacent ion scale flux ropes are observed using MMS data. We find that:

1. Intense and explosive filamentary currents in parallel and perpendicular directions are found inside the flux ropes.

2. The electron pitch angle distribution appears "X" like shape, and could be caused by the electron acceleration.

3. The filamentary current appears in the center of the "X" distribution.

The filamentary currents are important and are considered to be the evidence of secondary reconnection [Wang et al., 2020]. The observations in our study are important to reveal the particle acceleration and energy dissipation in magnetic reconnection.

How to cite: Xiao, Y., Yao, S., Guo, R., Shi, Q., Tian, A., Bai, S., and Liu, J.: MMS observations of explosive filamentary current within two adjacent ion scale flux ropes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15357, https://doi.org/10.5194/egusphere-egu21-15357, 2021.

11:53–12:30
Lunch break
Chairpersons: C.-Philippe Escoubet, Yulia Bogdanova
13:30–13:32
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EGU21-14077
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ECS
Zongshun Yue, Ji Liu, Shutao Yao, Quanqi Shi, Ruilong Guo, Anmin Tian, and Shichen Bai

Kinetic- scale magnetic hole (KSMH) is a kind of structure whose spatial scale is only or smaller than the ion gyroradius and the magnetic field intensity shows rapid decrease in the observation. Recently, with the improvement of high spatio-temporal resolution measurements, previous studies have revealed some physical processes at the small scale, like electron energization, energy dissipation, wave-particle interaction and the turbulence. However, these studies on KSMHs have not touched on the generation and evolution of these structures due to limitations in the analysis methods used. In this work, using a series of KSMHs events observed by MMS and a new method to analyze the size of the hole, we are studying the relationship between the size of KSMHs and their spatial position in the magnetosheath statistically, and try to find the headstream of this type of structures and reveal their evolution process when they propagate with plasma flow.

How to cite: Yue, Z., Liu, J., Yao, S., Shi, Q., Guo, R., Tian, A., and Bai, S.: The statistical research on the Kinetic- scale magnetic hole in magnetosheath, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14077, https://doi.org/10.5194/egusphere-egu21-14077, 2021.

13:32–13:37
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EGU21-8905
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ECS
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solicited
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Highlight
Jinghuan Li, Xuzhi Zhou, Fan Yang, Anton V. Artemyev, and Qiugang Zong

Magnetic cavities are sudden depressions of magnetic field strength widely observed in the space plasma environments, which are often accompanied by plasma density and pressure enhancement. To describe these cavities, a self-consistent kinetic model has been proposed as an equilibrium solution to the Vlasov-Maxwell equations. However, observations from the Magnetospheric Multi-Scale (MMS) constellation have shown the existence of helical magnetic cavities characterized by the presence of azimuthal magnetic field, which could not be reconstructed by the aforementioned model. Here, we take into account another invariant of motion, the canonical axial momentum, to construct the particle distributions and accordingly modify the equilibrium model. The reconstructed magnetic cavity shows excellent agreement with the MMS1 observations not only in the electromagnetic field and plasma moment profiles but also in electron pitch-angle distributions. With the same set of parameters, the model also predicts signatures of the neighboring MMS3 spacecraft, matching its observations satisfactorily.

How to cite: Li, J., Zhou, X., Yang, F., Artemyev, A. V., and Zong, Q.: Helical Magnetic Cavities: Kinetic Model and Comparison with MMS Observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8905, https://doi.org/10.5194/egusphere-egu21-8905, 2021.

13:37–13:39
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EGU21-14044
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ECS
Mengmeng Wang, Terry Z. Liu, Hui Zhang, Shichen Bai, Quanqi Shi, and Xiaoqiong Zhu

Foreshock bubbles (FBs) are kinetic phenomena that can form when a rotational discontinuity or a tangential discontinuity interacts with backstreaming ions in the Earth’s foreshock region. The scale of FBs can be up to 10 RE and the expansion speeds can be more than 100 km/s. The expansion of the hot ions contributes to the formation of a new shock on the trailing edge of an FB. Using MMS data, we analyze properties of the FB shock and the whistler precursor upstream of it. For the twelve FBs we analyzed, the FB shock normal has a strong X component in GSE coordinates and the quasi-parallel FB shocks are in favor of the generation of the whistler precursor. When the Mach number is larger than 3.5, the whistler precursor disappears. The wave forms are not phase standing since the angle of the wave vector and shock normal is larger than 9 degrees. They have frequencies near fLH and right-hand polarization with respect to the ambient magnetic field (in the spacecraft frame). The properties of the whistler precursor upstream of the FB shock are similar to those at interplanetary shocks.

How to cite: Wang, M., Liu, T. Z., Zhang, H., Bai, S., Shi, Q., and Zhu, X.: Properties of the whistler precursor upstream of the foreshock bubble shock: MMS observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14044, https://doi.org/10.5194/egusphere-egu21-14044, 2021.

13:39–13:41
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EGU21-12053
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ECS
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Highlight
Liudmila Rakhmanova, Maria Riazantseva, Georgy Zastenker, and Yuri Yermolaev

Development of the turbulent cascade inside the magnetosheath is known to be affected by the bow shock. Recently a number of studies showed various scenario of turbulent cascade modification at the bow shock including deviation from Kolmogorov scaling and additional damping of the kinetic-scale compressive fluctuations. Also, properties of probability distribution function may be modified behind the bow shock. However, factors which govern turbulence development in the magnetosheath remain unclear. Present study focuses on experimental analysis of the solar wind parameters which influence turbulence inside the magnetosheath. Analyzed data involves the combination of the solar wind parameters measured in L1 point by WIND spacecraft and Themis, Cluster and Spektr-R measurements behind the bow shock. Parameters of the frequency spectra of ion flux and/or magnetic field magnitude at frequency band from 0.01 to 2-10 Hz are considered such as slopes at magnetohydrodynamic and kinetic scales and the break frequency. Parameters of spectra are considered behind the bow shock of various topology i.e. for different mutual orientation of the interplanetary magnetic field and the local bow shock normal. Also, distance from the analyzed point to the bow shock nose is taken to the account. Obtained results point out that modification of the turbulent cascade at the bow shock is controlled not only by the bow shock topology but also by variability of the upstream solar wind plasma parameters and direction of the interplanetary magnetic field. In particular, Kolmogorov scaling often survives across the bow shock during periods of high-amplitude variations of plasma density and magnetic field magnitude in the solar wind. Also, increasing amplitude of northern interplanetary magnetic field results in steepening of spectra behind the bow shock.  

How to cite: Rakhmanova, L., Riazantseva, M., Zastenker, G., and Yermolaev, Y.: Solar wind and bow shock parameters affecting turbulence development inside the magnetosheath, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12053, https://doi.org/10.5194/egusphere-egu21-12053, 2021.

13:41–13:43
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EGU21-14451
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ECS
Jinyan Zhao, Quanqi Shi, Anmin Tian, Ruilong Guo, and Xiao-Chen Shen

A solar wind dynamic pressure increase/decrease leads to the compression/expansion of the Earth’s magnetosphere. In response, field-aligned currents, which are carried by precipitating or escaping plasma particles, are generated in the magnetosphere and in lead to variations in the auroral intensity. In this study, we investigate magnetospheric and ionospheric responses (including magnetospheric plasma vortex, ionospheric currents and aurorae) to a sudden decrease in solar wind dynamic pressure (SW Pdyn), which is critical for further understanding of the solar wind-magnetosphere-ionosphere coupling. We focused on a SW Pdyn decrease event that monitored by OMNI. A counter-clockwise plasma vortex was generated in the dusk side magnetosphere uncovered by using MHD simulation method and a clockwise equivalent ionospheric currents (EIC) vortex was generated in the dusk side ionosphere within about ten minutes after the pressure pulse arrival. Simultaneously, the observation results of Spherical Elementary Currents (SECs) showed that the EIC vortex region is dominated by downward field-aligned currents and the ground-based All-Sky Imager (ASI) observations in the vicinity of this EIC vortex showed that the aurorae diminished. These observations are consistent with the scenario proposed by Shi et al. (2014) that flow vortices in the magnetosphere generated by SW Pdyn sudden decrease carry downward field-aligned currents into the dusk side ionosphere, generating ionospheric current vortex and thereby modulating auroral activity on the dusk side.

How to cite: Zhao, J., Shi, Q., Tian, A., Guo, R., and Shen, X.-C.: Dusk side clockwise vortex generation and aurora intensity decrease after Solar Wind Dynamic Pressure Decrease, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14451, https://doi.org/10.5194/egusphere-egu21-14451, 2021.

13:43–13:45
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EGU21-12045
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ECS
Lei Cai, Anita Kullen, Tomas Karlson, Andris Vaivads, and Yongliang Zhang

The Defense Meteorological Satellite Program (DMSP) Special Sensor Ultraviolet Spectrographic Imager (SSUSI) has observed the large-scale high-latitude dayside aurora (HiLDA) during its long lifetime of hours. HiLDA has dynamical changes in form, size, location, and development of fine structures. However, the associated electrodynamics is not fully understood. In general, HiLDA occurs in the dayside polar cap during IMF By+ (By-) prevailing conditions in the sunlit northern (southern) hemisphere.  The prevailing conditions drive strong upward field-aligned current in the polar cap. Within the upward field-aligned current region, the field-aligned potential drop can be set up and accelerate the electrons, forming the monoenergetic electron precipitation (up to 10s keV) and producing HiLDA.

 

This study investigates the ionospheric flows, currents, and auroral precipitation in association with HiLDA, benified from the simultaneous measurements from the DMSP satellites, the AMPERE project, and ground-based magnetometers and SuperDARN coherent radars. We will show HiLDA interacts with duskside oval-aligned arcs or transpolar arcs. The interactions are associated with the cusp and the dayside reconnection at the duskside flank/high latitudes. The reconnection produces strong dusk-dawn convection with flow shears in the polar cap, which generates the upward Region 0 current. We find that HiLDA is formed in the high-latitude part of the upward Region 0 current. We apply the Knight relation and identify the lobe electrons (< 0.3 cm-3) as the source of HiLDA. The fine structures revealed in the emission intensity of HiLDA may suggest the uneven distribution of the electron density in the high-latitude lobe.

How to cite: Cai, L., Kullen, A., Karlson, T., Vaivads, A., and Zhang, Y.: Dayside ionospheric electrodynamics in association with high-latitude dayside aurora (HiLDA), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12045, https://doi.org/10.5194/egusphere-egu21-12045, 2021.

13:45–13:47
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EGU21-13879
Shuai Zhang, Jonathan Rae, Clare Watt, Alexander Degeling, Anmin Tian, Quanqi Shi, and Xiao-Chen Shen

Whistler mode chorus waves play a vital role in the Earth’s outer radiation belt dynamics through the cyclotron resonant pitch angle diffusion.     Recent numerical studies have shown that the temporal and spatial variability of wave growth parameters have universal importance for the diffusion process, which should be much larger than those in the traditional averaged diffusion model.       In the present study, we analyzed both the temporal and spatial coherence of chorus wave in a statistical method using data from the EMFISIS instrument onboard the Van Allen Probes A&B from November 2012 to July 2019. In total, we find 3,875 chorus wave events to calculate the correlation of wave amplitudes between Van Allen Probes A&B.      The results show that both the spatial and temporal correlation of chorus waves decrease significantly with increasing spacecraft separation and time lag, and the spatial and temporal coherence of chorus wave only last ~433 km and ~12 s. We also find that the spatial coherence of chorus waves is higher at L>6, on the dayside, or with a lower geomagnetic index (AL*), while the temporal coherence of chorus waves does not depend on the L-shell, geomagnetic index (AL*) or magnetic local time (MLT). Our results will increase the accuracy of modeling wave-particle interactions due to chorus waves.

How to cite: Zhang, S., Rae, J., Watt, C., Degeling, A., Tian, A., Shi, Q., and Shen, X.-C.: Determining the global coherence of chorus waves in the magnetosphere, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13879, https://doi.org/10.5194/egusphere-egu21-13879, 2021.

Global magnetospheric dynamics
13:47–13:57
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EGU21-7933
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solicited
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Highlight
Martin Archer, Michael Hartinger, Ferdinand Plaschke, David Southwood, and Lutz Rastaetter

Impulsive solar wind transients, such as pressure pulses and shocks, excite surface waves on the magnetopause. While much of this surface wave energy is advected downtail by the magnetosheath flow, recently it has been shown that some of these waves can be trapped locally forming a standing wave between the northern and southern ionospheres. It appears that this process can occur across most of the dayside magnetopause, however, it is not clear how these surface waves can resist the advective effect of the tailward flow. Through multispacecraft observations, global MHD simulations, and analytic MHD theory we show that azimuthally standing magnetopause surface waves are possible between 9-15h MLT. In this region, surface waves with Poynting vectors directed towards the subsolar point can exactly balance the advective effect of the magnetosheath flow, leading to no overall energy flow. Further downtail, however, the wave’s propagation cannot overcome advection and the usual tailward energy flow occurs. This trapping of magnetopause surface wave energy following the drivers of intense space weather may in turn have important implications on radiation belt, ionospheric, and auroral dynamics.

How to cite: Archer, M., Hartinger, M., Plaschke, F., Southwood, D., and Rastaetter, L.: Ripples going against the flow: How energy propagation determines the global structure of magnetopause surface waves, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7933, https://doi.org/10.5194/egusphere-egu21-7933, 2021.

13:57–13:59
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EGU21-5122
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ECS
Xiangcheng Dong, Malcolm Dunlop, Tieyan Wang, Jinsong Zhao, Huishan Fu, Zuzheng Chen, and Christopher Russell

Magnetospheric Multiscale (MMS) data are used to investigate the energy dissipation in a  reconnection diffusion region at the magnetopause. The four MMS spacecraft were separated by about 10 km such that comparative study between each spacecraft within the diffusion region can be implemented. Similar magnetic field and electric current behavior between each spacecraft indicates the formation of a quasi-homogeneous diffusion region structure. However, we find that the energy dissipation results between each spacecraft are different due to the temporal or spatial effect of the out-of-plane merging electric field (EM) during the dissipation region. Our study suggests that the intermittent energy dissipation in the reconnection dissipation region can be a common phenomenon, even under a stable diffusion region structure.

How to cite: Dong, X., Dunlop, M., Wang, T., Zhao, J., Fu, H., Chen, Z., and Russell, C.: MMS Observation of Intermittent Energy Dissipation in Magnetic Reconnection Diffusion Region, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5122, https://doi.org/10.5194/egusphere-egu21-5122, 2021.

13:59–14:01
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EGU21-1401
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ECS
Austin Brenner and Tuija Pulkkinen

Detailed 3D magnetopause surface is identified using field line and flow line tracing techniques on Space Weather Modeling Framework (SWMF) global magnetosphere simulation results. A total energy flux vector dominated by poynting flux is dotted with area element surface normals and integrated to determine energy transfer into the closed volume. Magnetopause characteristics, power and energy terms are compared with space weather indices such as Disturbance Storm-Time (Dst), Auroral Electrojet (AE), Cross Polar Cap Potential (CPCP) and emperical models such as Shue et al (1997) and Shue et al (1998) to investigate magnetopause dynamics. The storm event of Feb 18, 2014  is simulated with SWMF and analyzed. This event starts in the middle of a multi-CME impact, during a delay between the first and second CME's. While some preconditioning may have occured, it provides an excellent case for observing magnetopause variations. Results show close agreement with empirical models of integrated energy transfer through magnetopause surface. Energy accumulation inside magnetopause volume cuttoff at x=-20Re shows similar behavior to Dst.

How to cite: Brenner, A. and Pulkkinen, T.: Investigating magnetopause dynamics using global magnetosphere simulation , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1401, https://doi.org/10.5194/egusphere-egu21-1401, 2021.

14:01–14:03
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EGU21-5699
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ECS
Ravindra Desai, Jonathan Eastwood, Joseph Eggington, Mervyn Freeman, Martin Archer, Yuri Shprits, Nigel Meredith, Heli Hietala, Lars Mejnertsen, Jeremy Chittenden, and Richard Horne

Fast-forward interplanetary interplanetary shocks, as occur at the forefront of interplanetary coronal mass ejections and at corotating interaction regions, can rapidly compress the magnetopause inside the drift paths of electrons and protons, and expose geosynchonous satellites directly to the solar wind.  Here, we use Gorgon Global-MHD simulations to study the response of the magnetopause to different fast-forward interplanetary shocks, with strengths extending from the median shocks observed during solar minimum up to that representing an extreme space weather event. The subsequent magnetopause response can be characterised by three distinct phases; an initial acceleration as inertial forces are overcome, a rapid compression well-represented by a power law, and large-scale damped oscillatory motion of the order of an Earth radius, prior to reaching pressure-balance equilibrium. The subsolar magnetopause is found to oscillate with notable frequencies in the range of 2–13 mHz over several periods of diminishing amplitudes.  These results provide an explanation for similar large-scale magnetopause oscillations observed previously during the extreme events of August 1972 and March 1991 and highlight why static magnetopause models break down during periods of strong solar wind driving.

How to cite: Desai, R., Eastwood, J., Eggington, J., Freeman, M., Archer, M., Shprits, Y., Meredith, N., Hietala, H., Mejnertsen, L., Chittenden, J., and Horne, R.: Interplanetary Shock-driven Magnetopause Compressions in Gorgon Global-MHD Simulations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5699, https://doi.org/10.5194/egusphere-egu21-5699, 2021.

14:03–14:05
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EGU21-7632
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ECS
Michael Madelaire, Karl Laundal, Jone Reistad, Spencer Hatch, Anders Ohma, Stein Haaland, and Reham Elhawary

The geospace response to rapid changes in solar wind pressure results in a perturbation of the magnetospheric-ionospheric system. Ground magnetometer stations located at polar latitudes have long been known to measure a sudden impulse only minutes after a solar wind structure reaches the magnetopause.
Here a list of events associated with a step-like feature in the solar wind dynamic pressure between 1994 and 2020 is compiled based on in situ observations from ACE and Wind. Arrival time estimates are calculated using a simple propagation method and validated with a correlation analysis using SYM-H from low/mid latitude stations. A superposed epoch analysis is carried out to investigate the impact of season, interplanetary magnetic field orientation and other attributes pertaining to the interplanetary shock. All available ground magnetometer stations in SuperMAG, during each event, are used allowing for global coverage. 
Global data coverage is important for this kind of comparative analysis as it is needed to determine changes in the systems response due to e.g. season, which might lead to an improved understanding of the magnetospheric-ionospheric-thermospheric coupling.

How to cite: Madelaire, M., Laundal, K., Reistad, J., Hatch, S., Ohma, A., Haaland, S., and Elhawary, R.: The asymmetric geospace response to rapid changes in solar wind pressure, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7632, https://doi.org/10.5194/egusphere-egu21-7632, 2021.

14:05–14:07
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EGU21-8953
Gilbert Pi, Zdeněk Němeček, and Jana Šafránková

Magnetosheath is a major interface region between the solar wind and magnetosphere. The changes of solar wind parameters after the bow shock crossing and the phenomena near the magnetopause are intensively studied. However, spatial profiles of different pressure components across the magnetosheath are not comprehensively studied yet, especially in observations. The highly fluctuating sheath, variations of upstream conditions, and permanent motion of the magnetopause and bow shock complicate observational studies. In the present contribution, we use two different methods to obtain a typical magnetosheath profile under specific upstream conditions. One is the superposed epoch analysis of complete crossing events observed by the THEMIS mission. The second method is relocated the THEMIS observations into a normalized magnetosheath coordinate. By contrast to the result of MHD modeling, we found only a very weak difference between pressure profiles for southward and northward IMF. Our results show that the thermal pressure exhibits a peak near the magnetopause that is more pronounced under southward than under northward IMF. The magnetic pressures have a similar trend for both IMF polarities but the magnetic pressure increases faster toward the magnetopause for northward IMF than it does for southward IMF.

How to cite: Pi, G., Němeček, Z., and Šafránková, J.: Pressure Profiles in the Magnetosheath under Different Solar Wind Conditions , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8953, https://doi.org/10.5194/egusphere-egu21-8953, 2021.

14:07–14:09
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EGU21-9675
Suleiman Baraka, Olivier Le Contel, Lotfi Ben-Jaffel, and Bill Moore

The boundary between the solar wind (SW) and the Earth’s magnetosphere, named the magnetopause (MP), is highly dynamic. Its location and shape can vary as a function of different SW parameters such as density, velocity, and interplanetary magnetic field (IMF) orientations. We employ a 3D kinetic Particle-In-Cell (IAPIC) code to simulate these effects.  We investigate the impact of radial (B = Bx) and quasi-radial (Bz < Bx, By) IMF on the shape and size of Earth’s MP for a dipole tilt of 31o using both maximum density steepening and pressure system balance methods for identifying the boundary. We find that, compared with northward or southward-dominant IMF conditions, the MP position expands asymmetrically by 8 to 22% under radial IMF. In addition, we construct the MP shape along the tilted magnetic equator and the OX axes showing that the expansion is asymmetric, not global, stronger on the MP flanks, and is sensitive to the ambient IMF. Finally, we investigate the contribution of SW backstreaming ions by the bow shock to the MP expansion, the temperature anisotropy in the magnetosheath, and a strong dawn-dusk asymmetry in MP location.

How to cite: Baraka, S., Le Contel, O., Ben-Jaffel, L., and Moore, B.: How radial and quasi radial IMF impact the Earth's magnetopause's size, location, and shape. Does this impact generate Dawn-Dusk asymmetry in the magnetosheath?: Global 3D Kinetic Simulations. , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9675, https://doi.org/10.5194/egusphere-egu21-9675, 2021.

14:09–14:19
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EGU21-8153
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solicited
|
Highlight
Minna Palmroth, Urs Ganse, Markus Battarbee, Lucile Turc, Yann Pfau-Kempf, Maarja Bussov, Maxime Grandin, Andreas Johlander, Jonas Suni, Maxime Dubart, Kostis Papadakis, and Markku Alho

Numerical simulations are key in modern space physics, as they can be used as 1) context to data, 2) predict future behaviour of the system, 3) understand the system using unforeseen boundary conditions, and increasingly also in 4) discovering new phenomena that are hard to be observed using point-wise satellite measurements. Especially, the discovery of new phenomena pertains to global systems, where phenomena of interest may be initiated far away from the point of observations. The most typical method of simulating the global solar wind - magnetosphere - ionosphere system is based on magnetohydrodynamics (MHD), which is however not representing the actual plasma behaviour in locations where kinetic physics becomes important. Such regions are e.g., the foreshock - magnetosheath interaction, reconnection, and the inner magnetosphere.

Vlasiator is the world’s first and so far the only global simulation based on the hybrid-Vlasov approach that simulates the ion distributions accurately without noise. The simulation has, for computational reasons, been so far executed in 2D real space. Even so, the global 5D Vlasiator results have shown without a doubt that ion-kinetic effects cannot be neglected from the large scales, as small-scale phenomena affect large scales and vice versa. This scale coupling leads to phenomena that are not predicted using local simulations without proper boundary conditions, or with spacecraft measurements lacking the global context.

Here, we present the world’s first global 6-dimensional ion-kinetic global magnetospheric simulation run, accurate both locally and globally. The simulation box extends from the dayside to the nightside, and includes global dynamics and both dayside and nightside reconnection regions. We will investigate unambiguously for the first time the dayside magnetopause reconnection as driven by the kinetic variations in the magnetosheath, and tail reconnection as driven by magnetic flux from the dayside.

How to cite: Palmroth, M., Ganse, U., Battarbee, M., Turc, L., Pfau-Kempf, Y., Bussov, M., Grandin, M., Johlander, A., Suni, J., Dubart, M., Papadakis, K., and Alho, M.: Global 6-dimensional hybrid-Vlasov modelling of the magnetosphere: First Vlasiator results, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8153, https://doi.org/10.5194/egusphere-egu21-8153, 2021.

14:19–14:21
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EGU21-9370
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ECS
Maxime Dubart, Urs Ganse, Adnane Osmane, Andreas Johlander, Markus Battarbee, Markku Alho, Maarja Bussov, Harriet George, Maxime Grandin, Kostis Papadakis, Yann Pfau-Kempf, Jonas Suni, Lucile Turc, and Minna Palmroth

Numerical simulations are widely used in modern space physics and are an essential tool to understand or discover new phenomena which cannot be observed using spacecraft measurements. However, numerical simulations are limited by the space grid resolution of the system and the computational costs of having a high spatial resolution. Therefore, some physics may be unresolved in part of the system due to its low spatial resolution. We have previously identified, using Vlasiator, that the proton cyclotron instability is not resolved for grid cell sizes larger than four times the inertial length in the solar wind, for waves in the downstream of the quasi-perpendicular shock in the magnetosheath of a global hybrid-Vlasov simulation. This leads to unphysically high perpendicular temperature and a dominance of the mirror mode waves. In this study, we use high-resolution simulations to measure and quantify how the proton cyclotron instability diffuses and isotropizes the velocity distribution functions. We investigate the process of pitch-angle scattering during the development of the instability and propose a method for the sub-grid modelling of the diffusion process of the instability at low resolution. This allows us to model the isotropization of the velocity distribution functions and to reduce the temperature anisotropy in the plasma while saving computational resources.

How to cite: Dubart, M., Ganse, U., Osmane, A., Johlander, A., Battarbee, M., Alho, M., Bussov, M., George, H., Grandin, M., Papadakis, K., Pfau-Kempf, Y., Suni, J., Turc, L., and Palmroth, M.: Subgrid modelling of ion pitch-angle scattering for magnetosheath waves in a global hybrid-Vlasov simulation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9370, https://doi.org/10.5194/egusphere-egu21-9370, 2021.

14:21–14:23
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EGU21-10638
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ECS
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Highlight
Markku Alho, Markus Battarbee, Yann Pfau-Kempf, Urs Ganse, Lucile Turc, Andreas Johlander, Vertti Tarvus, Hongyang Zhou, Maxime Dubart, Maxime Grandin, Konstantinos Papadakis, Jonas Suni, Harriet George, Maarja Bussov, and Minna Palmroth

Models of the geospace plasma environment have been proceeding towards more realistic descriptions of the solar wind—magnetosphere interaction, from gas-dynamic to MHD and hybrid ion-kinetic models such as the state-of-the-art Vlasiator model. Advances in computational capabilities have enabled global simulations of detailed physics, but the electron scale has so far been out of reach in a truly global setting. 

In this work we present results from eVlasiator, an offshoot of the Vlasiator model, showing first results from a global 2D+3V kinetic electron geospace simulation. Despite truncation of some electron physics and use of ion-scale spatial resolution, we show that realistic electron distribution functions are obtainable within the magnetosphere and describe these in relation to MMS observations. Electron precipitation to the upper atmosphere from these velocity distributions is estimated.

How to cite: Alho, M., Battarbee, M., Pfau-Kempf, Y., Ganse, U., Turc, L., Johlander, A., Tarvus, V., Zhou, H., Dubart, M., Grandin, M., Papadakis, K., Suni, J., George, H., Bussov, M., and Palmroth, M.: A Global Survey of Geospace Electrons with eVlasiator: First Results, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10638, https://doi.org/10.5194/egusphere-egu21-10638, 2021.

14:23–14:25
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EGU21-3230
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Highlight
Graziella Branduardi-Raymont, Chi Wang, C. Philippe Escoubet, Steve Sembay, Eric Donovan, Lei Dai, Lei Li, Jing Li, David Agnolon, Walfried Raab, Colin Forsyth, Andy Read, Emma L. Spanswick, Jenny A. Carter, Hyunju Connor, Tianran Sun, Andrey Samsonov, and David G. Sibeck

A key link in the Sun – Earth connection is the solar wind coupling with the terrestrial magnetosphere. Mass and energy enter geospace via dayside magnetic reconnection; reconnection in the tail leads to release of energy and particle injection deep into the magnetosphere, causing geomagnetic substorms. The end product of these processes is the visual manifestation of variable auroral emissions. These have been observed both from the ground and from space, the latter for relatively short continuous periods of time. In situ measurements by a fleet of solar wind and magnetospheric missions, current and planned, can provide the most detailed observations of the plasma conditions both in the incoming solar wind and magnetospheric plasma. However, we are still unable to quantify the global effects of the drivers of Sun - Earth connections, and to monitor their evolution with time. This information is the key missing link for developing a comprehensive understanding of how the Sun gives rise to and controls the Earth's plasma environment and space weather. We are now able to take a novel approach to global monitoring of geospace: X-ray imaging of the magnetosheath and cusps is made possible by the X-ray emission produced in the process of solar wind charge exchange, first observed at comets, and subsequently found to occur in the vicinity of solar system planets, including the Earth's magnetosphere. This is where SMILE (Solar wind Magnetosphere Ionosphere Link Explorer) comes in.

SMILE is a novel self-standing mission dedicated to observing the solar wind – magnetosphere coupling at Earth via simultaneous X-ray imaging of the magnetosheath and polar cusps (large spatial scales at the magnetopause), UV imaging of global auroral distributions (mesoscale structures in the ionosphere) and in situ solar wind/magnetosheath plasma and magnetic field measurements. SMILE will provide scientific data on solar wind – magnetosphere interaction at the global level while monitoring it continuously for long, uninterrupted periods of time from a highly elliptical northern polar orbit.

SMILE is a collaborative mission between ESA and the Chinese Academy of Sciences that was selected in Nov. 2015, adopted into ESA’s Cosmic Vision Programme in March 2019, and is due for launch at the end of 2024. The novel science that SMILE will deliver, the ongoing technical developments and scientific preparations, and the current status of the mission, will be presented.

How to cite: Branduardi-Raymont, G., Wang, C., Escoubet, C. P., Sembay, S., Donovan, E., Dai, L., Li, L., Li, J., Agnolon, D., Raab, W., Forsyth, C., Read, A., Spanswick, E. L., Carter, J. A., Connor, H., Sun, T., Samsonov, A., and Sibeck, D. G.: Imaging solar-terrestrial interactions on the global scale: The SMILE mission, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3230, https://doi.org/10.5194/egusphere-egu21-3230, 2021.

14:25–14:27
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EGU21-2860
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Highlight
Elena Kronberg, Fabio Gastaldello, Stein Haaland, Artem Smirnov, Max Berrendorf, Simona Ghizzardi, Kip Kuntz, Nithin Sivadas, Robert Allen, Andrea Tiengo, Raluca llie, Yu Huang, and Lynn Kistler

One of the major and unfortunately unforeseen sources of background for the current generation of X-ray telescopes flying mainly in the magnetosphere are soft protons with few tens to hundreds of keV concentrated. One such telescope is the X-ray Multi-Mirror Mission (XMM-Newton) by ESA. Its observing time lost due to the contamination is  about 40%. This affects all the major broad science goals of XMM, ranging from cosmology to astrophysics of neutron stars and black holes. The soft proton background could dramatically impact future X-ray missions such Athena and SMILE missions. Magnetopsheric processes that trigger this background are still poorly understood. We use a machine learning approach to delineate related important parameters and to develop a model to predict the background contamination using 12 years of XMM observations. As predictors we use the location of XMM, solar and geomagnetic activity parameters. We revealed that the contamination is most strongly related to the distance in southern direction, ZGSE, (XMM observations were in the southern hemisphere), the solar wind velocity and the location on the magnetospheric magnetic field lines. We derived simple empirical models for the best two individual predictors and a machine learning model which utilizes an ensemble of the predictors (Extra Trees Regressor) and gives better performance. Based on our analysis, future X-Ray missions in the magnetosphere should minimize observations during  times  associated with high solar wind speed  and avoid closed magnetic field lines, especially at the dusk flank region at least in the southern hemisphere. 

How to cite: Kronberg, E., Gastaldello, F., Haaland, S., Smirnov, A., Berrendorf, M., Ghizzardi, S., Kuntz, K., Sivadas, N., Allen, R., Tiengo, A., llie, R., Huang, Y., and Kistler, L.: Prediction and understanding of soft proton contamination in XMM-Newton: a machine learning approach, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2860, https://doi.org/10.5194/egusphere-egu21-2860, 2021.

14:27–14:29
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EGU21-8329
Andrey Samsonov, Jennifer A. Carter, Graziella Branduardi-Raymont, and Steven Sembay

On 16-17 June 2012, an interplanetary coronal mass ejection with an extremely high solar wind density (~100 cm-3) and mostly strong northward (or eastward) interplanetary magnetic field (IMF) interacted with the Earth’s magnetosphere. We have simulated this event using global MHD models. We study the magnetospheric response to two solar wind discontinuities. The first is characterized by a fast drop of the solar wind dynamic pressure resulting in rapid magnetospheric expansion. The second is a northward IMF turning which causes reconfiguration of the magnetospheric-ionospheric currents. We discuss variations of the magnetopause position and locations of the magnetopause reconnection in response to the solar wind variations. In the second part of our presentation, we present simulation results for the forthcoming SMILE (Solar wind Magnetosphere Ionosphere Link Explorer) mission. SMILE is scheduled for launch in 2024. We produce two-dimensional images that derive from the MHD results of the expected X-ray emission as observed by the SMILE Soft X-ray Imager (SXI). We discuss how SMILE observations may help to study events like the one presented in this work.

How to cite: Samsonov, A., Carter, J. A., Branduardi-Raymont, G., and Sembay, S.: MHD simulations of magnetospheric response to a strong solar wind density pulse, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8329, https://doi.org/10.5194/egusphere-egu21-8329, 2021.

14:29–15:00
Break
Chairpersons: Andrey Samsonov, Yulia Bogdanova
15:30–15:32
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EGU21-15314
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ECS
Michaela Mooney, Colin Forsyth, Mike Marsh, and Jonathan Rae

Identifying the plasmapause location is crucial for forecasting and modelling the radiation belts, as well as larger scale models of the magnetosphere. The ionospheric footpoints of the plasmapause are thought to map to the equatorward edge of the diffuse aurora, with the first direct observation of an undulation of the plasmapause boundary and corresponding auroral features reported by He et al. (2020). Despite the importance of the plasmapause location, we do not have global observations of the plasmapause location.

We provide a new statistical model of the plasmapause location determined from mapping the equatorward boundary of the observed auroral oval out to the inner magnetosphere. The model uses the equatorward boundary of the auroral oval determined from far-ultraviolet observations from the IMAGE spacecraft from Longden et al. (2010) to provide a statistical estimate of the plasmapause location for different levels of geomagnetic activity. Comparing the results of the statistical plasmapause model to other more direct measurements of the plasmapause shows a good agreement in the nightside local time sectors. 

The results of this analysis show that the equatorward boundary of the auroral oval statistically maps closely to the plasmapause boundary the nightside sectors and provides an alternative use for global auroral image data from the upcoming SMILE mission. 

How to cite: Mooney, M., Forsyth, C., Marsh, M., and Rae, J.: Identifying the plasmapause location from global auroral image data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15314, https://doi.org/10.5194/egusphere-egu21-15314, 2021.

15:32–15:34
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EGU21-9070
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Highlight
Steve Milan, Jenny Carter, Gemma Bower, Suzie Imber, Larry Paxton, Brian Anderson, Marc Hairston, and Benoit Hubert

We propose a mechanism for the formation of the horse-collar auroral configuration common during periods of strongly northwards interplanetary magnetic field, invoking the action of dual-lobe reconnection (DLR).  Auroral observations are provided by the Imager for Magnetopause-to-Auroras Global Exploration (IMAGE) satellite and spacecraft of the Defense Meteorological Satellite Program (DMSP).  We also use ionospheric flow measurements from DMSP and polar maps of field-aligned currents (FACs) derived from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE).  Sunward convection is observed within the dark polar cap, with antisunwards flows within the horse-collar auroral region, together with the NBZ FAC distribution expected to be associated with DLR.  We suggest that newly-closed flux is transported antisunwards and to dawn and dusk within the reverse lobe cell convection pattern associated with DLR, causing the polar cap to acquire a teardrop shape and weak auroras to form at high latitudes.  Horse-collar auroras are a common feature of the quiet magnetosphere, and this model provides a first understanding of their formation, resolving several outstanding questions regarding the nature of DLR and the magnetospheric structure and dynamics during northwards IMF.  The model can also provide insights into the trapping of solar wind plasma by the magnetosphere and the formation of a low-latitude boundary layer and cold, dense plasma sheet.  We speculate that prolonged DLR could lead to a fully closed magnetosphere, with the formation of horse-collar auroras being an intermediate step.

How to cite: Milan, S., Carter, J., Bower, G., Imber, S., Paxton, L., Anderson, B., Hairston, M., and Hubert, B.: Dual-lobe reconnection and horse-collar auroras, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9070, https://doi.org/10.5194/egusphere-egu21-9070, 2021.

15:34–15:36
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EGU21-10704
Jone Peter Reistad, Karl Magnus Laundal, Anders Ohma, Nikolai Østgaard, Spencer Hatch, Stein Haaland, and Evan Thomas

Lobe reconnection is usually considered to play an important role in geospace dynamics only when the Interplanetary Magnetic Field (IMF) is mainly northward. This is because the most common signature of lobe reconnection is the strong sunward convection in the polar cap ionosphere observed during these conditions. During more typical conditions, when the IMF is mainly in a dawn-dusk direction, plasma flows initiated by dayside as well as lobe reconnection map to high latitude ionospheric locations in close proximity to each other. This has been emphasized in the literature earlier, mainly on a conceptual level, but quantifying the relative importance of lobe reconnection to the observed ionospheric convection is highly challenging during these IMF By dominated conditions, since one has to identify and distinguish these regions. By normalizing the ionospheric convection (observed by SuperDARN) to the polar cap boundary (inferred from simultaneous AMPERE observations), we are able to do this separation, allowing us to quantify the relative contribution of both lobe reconnection and dayside/nightisde reconnection to the ionospheric convection pattern. Using this segmentation technique we can get new quantitative insights into the importance of the various mechanisms that affect the lobe reconnection rate. In this presentation we will describe the technique and show results of analysis of periods when the IMF is mainly in the dawn-dusk direction. Our quantification of the average lobe reconnection rate during various conditions yields quantitative knowledge of the importance of the lobe reconnection process, which can act independently in the two hemispheres. We will specifically constrain the influence from parameters such as the dipole tilt angle and the product of IMF transverse component and solar wind velocity.

How to cite: Reistad, J. P., Laundal, K. M., Ohma, A., Østgaard, N., Hatch, S., Haaland, S., and Thomas, E.: Quantifying the lobe reconnection rate during dominant IMF By periods, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10704, https://doi.org/10.5194/egusphere-egu21-10704, 2021.

15:36–15:38
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EGU21-13768
Formation and decay of a transpolar arc during a major magnetic storm onset
(withdrawn)
Tuija Pulkkinen, Shannon Hill, Qusai Al Shidi, Austin Brenner, and Shasha Zou
15:38–15:40
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EGU21-7493
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ECS
Amalie Ø. Hovland, Kjellmar Oksavik, Jone P. Reistad, and Marc R. Hairston

This multi-instrument case study investigates the electrodynamics surrounding polar cap auroral arcs. A long-lasting auroral arc is observed in the high latitude dusk-sector at ~80° Apex latitude in the northern hemisphere. Ion drift measurements from the SSIES system on the DMSP spacecraft have been combined with multiple ground-based observations. Line of sight velocity data from three polar latitude high-frequency Super Dual Auroral Radar Network (SuperDARN) radars show mesoscale structure in the ionospheric convection in the region surrounding the arc. The convection electric field in this region is modelled using a Spherical Elementary Convection Systems (SECS) technique, using curl-free basis functions only. The result is a regional model of the ionospheric convection based on the fairly dense and distributed flow observations and the curl-free constraint. The model is compared to optical data of the auroral arc from two high latitude Redline Emission Geospace Observatory (REGO) all-sky imagers as well as UV images and particle measurements from the DMSP spacecraft to describe the local electrodynamics in the vicinity of the high latitude arc throughout the event.

How to cite: Hovland, A. Ø., Oksavik, K., Reistad, J. P., and Hairston, M. R.: Electrodynamics surrounding polar cap auroral arcs, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7493, https://doi.org/10.5194/egusphere-egu21-7493, 2021.

15:40–15:42
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EGU21-9117
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ECS
Margot Decotte, Karl M. Laundal, Spencer Hatch, and Jone Reistad

We present a method for tracking the evolution of the auroral boundaries on the dawn and dusk flanks during magnetospheric substorms by using a combined database of auroral zone boundaries derived from DMSP and POES/MetOp satellite particle measurements. Auroral boundaries can be identified by the Kilcommons et al. (2017) algorithm which use electron energy fluxes from the DMSP spectrometer (SSJ instrument). We show how auroral boundaries may also be obtained from precipitating electron observations from the POES/MetOp Total Energy Detector (TED) instrument by subjecting the TED electron measurements to an algorithm similar to that presented by Kilcommons et al. (2017). Boundaries derived from the two satellite missions are similar, suggesting that the technique for auroral oval boundary identification is physically meaningful.

How to cite: Decotte, M., Laundal, K. M., Hatch, S., and Reistad, J.: Substorm evolution of the auroral zone boundaries on the dawn and dusk flanks: DMSP and POES/MetOp observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9117, https://doi.org/10.5194/egusphere-egu21-9117, 2021.

15:42–15:44
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EGU21-11400
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ECS
Andreas Lysaker Kvernhaug, Karl M. Laundal, and Jone P. Reistad

According to the expanding-contracting polar cap paradigm, dayside and nightside reconnection control magnetosphere-ionosphere dynamics at high latitudes by increasing or decreasing the open flux respectively. The dayside reconnection rate can be estimated using parameters measured in the solar wind, but there is no reliable and available proxy for the nightside reconnection rate. We want to remedy this by using AMPERE to estimate a time series of open flux content. The AMPERE data set originates from the global Iridium satellite system, enabling continuous measurements of the field-aligned Birkeland currents, from which the open magnetic flux of the polar caps can be derived. These estimates will be used to derive empirical relationships with available measurements on the ground and in the solar wind. This work can also help improve estimates of dayside reconnection rates.

How to cite: Kvernhaug, A. L., Laundal, K. M., and Reistad, J. P.: Empirical relationship between nightside reconnection rate and solar wind / geomagnetic measurements, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11400, https://doi.org/10.5194/egusphere-egu21-11400, 2021.

15:44–15:46
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EGU21-3372
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ECS
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Highlight
Reham Elhawary, Karl Laundal, Jone Reistad, Anders Ohma, Spencer Hatch, and Michael Madelaire

Substorm onset location varies over a range of magnetic local time (MLT) and magnetic latitudes (MLat). It is well known that about 5% of the variation in onset MLT can be explained by variations in interplanetary magnetic field orientation and dipole tilt angle. Both parameters introduce an azimuthal component in the magnetic field in the magnetosphere such that the projection of the onset MLT in the ionosphere is shifted. The MLT of the onset near the magnetopsheric equatorial plane is even less predictable. Recent studies have suggested that gradients in the ionospheric Hall conductance lead to a duskward shift of tail dynamics, which could also influence the location of substorm onset. Our goal is to test these ideas by quantifying the dependence of the spatial variation of the onset location on external and internal conditions. We focus on the correlation between the substorm onset location with conditions prior to the onset, such as the interplanetary magnetic field By component, dipole tilt angle, and estimates of the Hall conductance. Linear regression analysis is used to determine the substorm onset location dependence on the proposed variables.

How to cite: Elhawary, R., Laundal, K., Reistad, J., Ohma, A., Hatch, S., and Madelaire, M.: Parameters controlling the substorm onset location, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3372, https://doi.org/10.5194/egusphere-egu21-3372, 2021.

15:46–15:48
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EGU21-10541
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ECS
Sina Sadeghzadeh, Jian Yang, and Ameneh Mousavi

Astrophysical plasmas are collisionless and correlated systems in which particles are out of thermal equilibrium and can be characterized by non-Maxwellian distribution functions. Amongst those nonthermal distribution functions, the kappa distribution has been widely used and satisfactorily modeled numerous space plasma environments such as ring current and plasma sheet. The particles spectra observed by detector measurements onboard the satellites (e.g., Time History of Events and Macroscale Interactions during Substorms (THEMIS)) indicate that the energy fluxes of plasma sheet particles can be fitted well by the kappa distribution (or combinations thereof). Besides, many empirical models have also used such distributions to estimate fluxes at different energies. Statistically, in the RCM simulations, at all times, even geomagnetically quiet conditions, the initial plasma distribution is assumed to be a kappa function with κ≈6. However, based on the flux spectra constructed by THEMIS data, the kappa index has a significant dawn-dusk asymmetry and a clear dependency on the geocentric distance (R) and the magnetic local time (MLT). Using the averaged RCMI calculated energy fluxes in the equatorial plane we intend to analyze the spatial distribution of the spectral index both for ions (κi) and electrons (κe) in this region and compare the simulation results with observations.

How to cite: Sadeghzadeh, S., Yang, J., and Mousavi, A.: Spatial variation of the kappa index in the Earth’s plasma sheet: RCMI results, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10541, https://doi.org/10.5194/egusphere-egu21-10541, 2021.

15:48–15:50
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EGU21-14489
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ECS
Louis Richard, Yuri Khotyaintsev, Daniel Graham, Olivier Le Contel, Ian Cohen, Drew Turner, Barbara Giles, Per-Arne Lindqvist, and Christopher Russell

We investigate an earthward bursty bulk flow (BBF) observed by the Magnetospheric Multiscale (MMS) spacecraft in the Earth’s magnetotail (XGSM ~ -23.88 RE, YGSM ~ 6.72 RE, ZGSM ~ 4.06 RE). At  the leading edge of the BBF we observe a complex magnetic field structure. In particular, within this region we identify multiple dipolarization fronts (DFs) and large amplitude oscillations of the magnetic field BX, which correspond to a long wavelength current sheet flapping motion. Within the DFs, we observe increased fluxes of energetic ions and electrons. We investigate the trapping of the ions between two consecutive DFs. We discuss the ion acceleration mechanism and the adiabaticity of the ion energisation process.

How to cite: Richard, L., Khotyaintsev, Y., Graham, D., Le Contel, O., Cohen, I., Turner, D., Giles, B., Lindqvist, P.-A., and Russell, C.: Turbulent Plasma Jet Fronts and Related Ion Acceleration, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14489, https://doi.org/10.5194/egusphere-egu21-14489, 2021.

15:50–15:52
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EGU21-13957
Jun Liang, Dmytro Sydorenko, Eric Donovan, and Robert Rankin

Photoelectrons are produced by solar Extreme Ultraviolet radiation and contribute significantly to the ionization and heat balances in planetary upper atmospheres. They are also the source of dayglow emissions, whose intensities may become comparable to weak or moderate dayside auroras. Proper modeling of photoelectrons and dayglow components is desirable for global auroral imaging, one of the core objectives of the SMILE mission. In many previous studies and model simulations, the transport effects of photoelectrons are neglected, so that the photoelectron distribution is controlled by a balance between local production and energy degradation. However, photoelectrons, when generated, can move along the magnetic field line. In particular, some of the photoelectrons may precipitate into the conjugate dark hemisphere and induce auroral-like emissions there, which was reported in realistic observations [Kil et al., 2020]. As a part of the SMILE Ultraviolet imager (UVI) model platform, we have recently developed an auroral/dayglow model that takes into account the interhemispheric transport of photoelectrons and/or secondary electrons, as well as their interaction with the ionosphere/thermosphere. In this study, we report the model simulation of the photoelectron generation and transport, and their induced UV emissions in both the dayside and nightside atmosphere. The simulation results are found to be in reasonable agreement with the realistic SSUSI/GUVI observations.

How to cite: Liang, J., Sydorenko, D., Donovan, E., and Rankin, R.: Photoelectron transport and associated Far Ultraviolet emissions: Model simulation and comparison with observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13957, https://doi.org/10.5194/egusphere-egu21-13957, 2021.

15:52–15:54
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EGU21-7607
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ECS
Simon Walker, Margot Decotte, Karl Laundal, Jone Reistad, Anders Ohma, and Spencer Hatch

By utilising measurements from twenty ground magnetometer stations in Fennoscandia, divergence-free ionospheric currents above this region are modelled using spherical elementary currents (SECS). New modelling techniques are implemented that coerce the model to find a solution that resembles the resolvable ionospheric currents. The divergence-free currents are evaluated along the 105o magnetic meridian covering a period of almost 20 years with a resolution of 1 minute, as a result of the magnetometers chosen. From these sheet current density latitude profiles, the boundaries of the auroral electrojet are identified. After performing a large statistical analysis it is found that there is a significant IMF By effect on the poleward boundary of the electrojets during the Summer but not during the Winter. We suggest that this seasonal effect can be attributed to the effects of lobe reconnection on the extent of currents in the auroral electrojets. Further work is done to compare the SECS derived electrojet boundaries with particle precipitation data from low orbit satellites.

How to cite: Walker, S., Decotte, M., Laundal, K., Reistad, J., Ohma, A., and Hatch, S.: Electrojet poleward boundary variations with IMF By and season, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7607, https://doi.org/10.5194/egusphere-egu21-7607, 2021.

15:54–15:56
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EGU21-5298
Dong Wei, Malcolm Dunlop, Junying Yang, Xiangcheng Dong, Yiqun Yu, and Tieyan Wang

During geomagnetically disturbed times the surface geomagnetic field often changes abruptly, producing geomagnetically induced currents (GICs) in a number of ground based systems. There are, however, few studies reporting GIC effects which are driven directly by bursty bulk flows (BBFs) in the inner magnetosphere. In this study, we investigate the characteristics and responses of the magnetosphere-ionosphere-ground system during the 7 January 2015 storm by using a multi-point approach which combines space-borne measurements and ground magnetic observations. During the event, multiple BBFs are detected in the inner magnetosphere while the magnetic footprints of both magnetospheric and ionospheric satellites map to the same conjugate region surrounded by a group of magnetometer ground stations. It is suggested that the observed, localized substorm currents are caused by the observed magnetospheric BBFs, giving rise to intense geomagnetic perturbations. Our results provide direct evidence that the wide-range of intense dB/dt (and dH/dt) variations are associated with a large-scale, substorm current system, driven by multiple BBFs.

How to cite: Wei, D., Dunlop, M., Yang, J., Dong, X., Yu, Y., and Wang, T.: Intense dB/dt variations driven by near-Earth Bursty Bulk Flows (BBFs): A case study, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5298, https://doi.org/10.5194/egusphere-egu21-5298, 2021.

15:56–17:00