This open session traditionally invites presentations on all aspects of the Earth’s magnetospheric physics, including the magnetosphere and its boundary layers, magnetosheath, bow shock and foreshock as well as solar wind-magnetosphere-ionosphere coupling. We welcome contributions on various aspects of magnetospheric observations, remote sensing of the magnetosphere’s processes, modelling and theoretical research. The presentations related to the current and planned space missions and to the value-added data services are also encouraged. This session is suitable for any contribution which does not fit more naturally into one of the specialised sessions and for contributions of wide community interest.

Convener: Yulia Bogdanova | Co-convener: C.-Philippe Escoubet
| Attendance Tue, 05 May, 08:30–10:15 (CEST)

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Chat time: Tuesday, 5 May 2020, 08:30–10:15

Chairperson: Yulia Bogdanova, C.-Philippe Escoubet
D2945 |
Lucile Turc, Vertti Tarvus, Andrew Dimmock, Markus Battarbee, Urs Ganse, Andreas Johlander, Maxime Grandin, Yann Pfau-Kempf, Maxime Dubart, and Minna Palmroth

The magnetosheath is the region bounded by the bow shock and the magnetopause which is home to shocked solar wind plasma. At the interface between the solar wind and the magnetosphere, the magnetosheath plays a key role in the coupling between these two media. Previous works have revealed pronounced dawn-dusk asymmetries in the magnetosheath properties, with for example the magnetic field strength and flow velocity being larger on the dusk side, while the plasma is denser, hotter and more turbulent on the dawn side. The dependence of these asymmetries on the upstream parameters remains however largely unknown. One of the main sources of these asymmetries is the bow shock configuration, which is typically quasi-parallel on the dawn side and quasi-perpendicular on the dusk side of the terrestrial magnetosheath because of the Parker-spiral orientation of the interplanetary magnetic field (IMF) at Earth. Most of these previous studies rely on collections of spacecraft measurements associated with a wide range of upstream conditions that have been processed to obtain the average values of the magnetosheath parameters. In this work, we use a different approach and quantify the magnetosheath asymmetries in global hybrid-Vlasov simulations performed with the Vlasiator model. We concentrate on three parameters: the magnetic field strength, the plasma density and the flow velocity. We find that the Vlasiator model reproduces accurately the polarity of the asymmetries, but that their level tends to be higher than in spacecraft measurements, probably due to the different processing methods. We investigate how the asymmetries change when the IMF becomes more radial and when the Alfvén Mach number decreases. When the IMF makes a 30° angle with the Sun-Earth line instead of 45°, we find a stronger magnetic field asymmetry and a larger variability of the magnetosheath density. In contrast, a lower Alfvén Mach number leads to a decrease of the magnetic field asymmetry level and of the variability of the magnetosheath density and velocity, likely due to weaker foreshock processes.

How to cite: Turc, L., Tarvus, V., Dimmock, A., Battarbee, M., Ganse, U., Johlander, A., Grandin, M., Pfau-Kempf, Y., Dubart, M., and Palmroth, M.: Asymmetries in the Earth's dayside magnetosheath: results from global hybrid-Vlasov simulations, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9211, https://doi.org/10.5194/egusphere-egu2020-9211, 2020.

D2946 |
| solicited
Huishan Fu

During magnetic reconnection, magnetic energy is explosively converted to particle energy and consequently electrons are accelerated to hundreds of keV that are dangerous to spacecraft and astronauts. To date, how and where the acceleration happens during reconnection is still unknown. Also, how efficient can the acceleration be remains a puzzle. Using spacecraft measurements (e.g., Cluster and MMS) and numerical simulations, many attempts have been made to answer these questions during the last twenty years. In this talk, I will briefly review these progresses and then show our recent results in understanding these issues. Specifically, I will (1) report a super-efficient electron acceleration by magnetic reconnection in the Earth’s magnetotail, during which electron fluxes are enhanced by 10000 times within 30 seconds; (2) discuss the mechanisms leading to super-efficient electron acceleration; (3) report the first evidence of electron acceleration at a reconnecting magnetopause, during which the acceleration process is nonadiabatic; and (4) report electron acceleration in the

How to cite: Fu, H.: Energetic electron acceleration during magnetic reconnection, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1945, https://doi.org/10.5194/egusphere-egu2020-1945, 2020.

D2947 |
Jean Berchem, Giovanni Lapenta, Robert Richard, William Paterson, and C. Philippe Escoubet

Increasingly sophisticated instruments and simulations have revealed a wide variety of plasma processes and multiscale structures at the dayside magnetopause. In this presentation, we focus on the origins and evolution of the plasma populations observed in the magnetopause boundary layers. We present the results of Particle-In-Cell (PIC) simulations encompassing large volumes of the dayside magnetosphere. The implicit 3D PIC code used in the study was initialized from a global MHD state of the magnetosphere for southward interplanetary field conditions.  Three-dimensional plots of the perpendicular slippage indicates that reconnection occurs over most of the dayside magnetopause. However, the simulation reveals that the reconnection region has a much more filamentary structure than the X-line expected from the extrapolation of 2D models and that multiscale structures thread the reconnection outflow. In particular, the simulation indicates the formation of multiple layers of electrons with significant field-aligned velocities along the main magnetopause current layer. We use velocity distribution functions at different locations in the reconnection outflow to characterize the origins and evolution of the electron and ionpopulations of the magnetosheath and magnetospheric boundary layers and compare them with observations from the MMS and Cluster spacecraft.

How to cite: Berchem, J., Lapenta, G., Richard, R., Paterson, W., and Escoubet, C. P.: Origins and Evolution of the Electron and Ion Populations of the Magnetopause’s Boundary Layers, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5786, https://doi.org/10.5194/egusphere-egu2020-5786, 2020.

D2948 |
Francesca Di Mare, Luca Sorriso-Valvo, Alessandro Retino', Francesco Malara, and Hiroshi Hasegawa

The turbulence at the interface between the solar wind and the Earth’s magnetosphere, mediated by the magnetopause and its boundary layer are investigated by using Geotail and THEMIS spacecraft data during ongoing Kelvin-Helmholtz instability (KHI). The efficient transfer of energy across scales for which the turbulence is responsible, achieves the connection between the macroscopic flow and the microscopic dissipation of this energy. This boundary layer is thought to be the result of the observed plasma transfer, driven by the development of the KHI, originating from the velocity shear between the solar wind and the almost static near-Earth plasma. A collection of 20 events spatially located on the tail-flank magnetopause, selected from previously studied by Hasegawa et al. 2006 and Lin et al. 2014, have been tested against standard diagnostics for intermittent turbulence. In light of the results obtained, we have investigated the behaviour of several parameters as a function of the progressive departure along the Geocentric Solar Magnetosphere coordinates, which roughly represent the direction in which we expect the KHI vortices to evolve towards fully developed turbulence. It appears that a fluctuating behaviour of the parameters exist, visible as a decreasing, quasi-periodic modulation with an associated periodicity, estimated to correspond to approximately 6.4 Earth Radii. Such observed wavelength is consistent with the estimated vortices roll-up wavelength reported in the literature for these events. If the turbulence is pre-existent, it is possible that the KHI modulates its properties along the magnetosheath, as we observed. On the other hand, if we assume that the KHI has been initiated near the magnetospheric nose and develops along the flanks, then the different intervals we study may be sampling the plasma at different stages of evolution of the KH-generated turbulence, after the instability has injected energy in a cascading process as large-scale structures.

How to cite: Di Mare, F., Sorriso-Valvo, L., Retino', A., Malara, F., and Hasegawa, H.: Evolution of Turbulence in the Kelvin–Helmholtz Instability mediated by the Magnetopause and its Boundary Layer, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21014, https://doi.org/10.5194/egusphere-egu2020-21014, 2020.

D2949 |
Stefan Kiehas, Andrei Runov, Vassilis Angelopoulos, and Daniil Korovinskiy

We perform a five year statistical study of fast flows in the Earth's magnetotail observed by ARTEMIS to investigate their occurrence rate, dawn-dusk asymmetry and relation with magnetospheric substorms. Almost half of the observed flows are directed earthward and their percentage decreases with increasing flow speed. While no clear dawn-dusk asymmetry is observed for earthward directed flows, about 60% of the tailward flows occur in the dusk sector. For tailward flows this asymmetry is similar for different AL thresholds. However, earthward flows become strongly asymmetric towards dusk for higher AL thresholds. A correlation of flow events with the AL index also shows a clear correlation of tailward flows with a decrease in AL, while such a correlation can not be seen for earthward flows. 

How to cite: Kiehas, S., Runov, A., Angelopoulos, V., and Korovinskiy, D.: Magnetotail flows near lunar orbit and their relation to substorms, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11901, https://doi.org/10.5194/egusphere-egu2020-11901, 2020.

D2950 |
Andrey Malykhin, Elena Grigorenko, Elena Kronberg, and Patrick Daly

Usually, for the plasma pressure estimation in the plasma sheet  ion observations in the energy range up to ~40 keV are used. However, the thermal part of the distribution function can pass beyond the high energy threshold of an instrument during active events like dipolarizations. In such cases the entire ion population is not measured and the ion pressure can be underestimated. We study this problem by using Cluster mission observations provided  by two instruments: thermal plasma instrument - CODIF (up to 38 keV) and suprathermal instrument - RAPID (from 40 up to 1500 keV). We analyzed 11 dipolarization events and showed that in all events the maximum of ion energy flux was shifted to high energy threshold of CODIF instrument. Simultaneously, the energy flux increase in suprathermal energy range was observed by RAPID. For H+ and O+ ion components we calculate the pressure of suprathermal population and showed that the total pressure estimated by using both CODIF and RAPID instruments at some intervals exceeds the pressure estimated only from CODIF data up to 5 times. The superposed epoch analysis applied to 11 dipolarization events from our data base showed that the total pressure of H+ and O+ ion components can be in 2-5 times underestimated in the course of dipolarization.

How to cite: Malykhin, A., Grigorenko, E., Kronberg, E., and Daly, P.: Сomparison of ion pressure variations derived from Cluster/CODIF and the combined Cluster/CODIF&RAPID data during prolonged dipolarizations in the near Earth magnetotail , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1488, https://doi.org/10.5194/egusphere-egu2020-1488, 2020.

D2951 |
| Highlight
Graziella Branduardi-Raymont, Chi Wang, C. Philippe Escoubet, Steve Sembay, Eric Donovan, Lei Dai, Lei Li, Jing Li, David Agnolon, Walfried Raab, Jonathan Rae, Andy Read, Emma L. Spanswick, Jenny A. Carter, Hyunju Connor, Tianran Sun, Andrey Samsonov, and David G. Sibeck

The coupling between the solar wind and the Earth's magnetosphere-ionosphere system, and the geospace dynamics that result, comprise some of the key questions in space plasma physics. In situ measurements by a fleet of solar wind and magnetospheric missions, current and planned, can provide the most detailed observations of the Sun-Earth connections. However, we are still unable to quantify the global effects of the drivers of such 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.

SMILE (Solar wind Magnetosphere Ionosphere Link Explorer) is a novel self-standing mission dedicated to observing the solar wind - magnetosphere coupling 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. 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 the Earth's magnetosphere. One of the science aims of SMILE is to track the substorm cycle, via X-ray imaging on the dayside and by following its consequences on the nightside with UV imaging. 

SMILE is a collaborative mission between ESA and the Chinese Academy of Sciences (CAS) that was selected in November 2015, adopted into ESA’s Cosmic Vision Programme in March 2019, and is due for launch at the end of 2023. The science that SMILE will deliver, as well as 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., Rae, J., Read, A., Spanswick, E. L., Carter, J. A., Connor, H., Sun, T., Samsonov, A., and Sibeck, D. G.: The SMILE mission: A novel way to explore solar-terrestrial interactions , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10783, https://doi.org/10.5194/egusphere-egu2020-10783, 2020.

D2952 |
Markus Battarbee, Xóchitl Blanco-Cano, Lucile Turc, Primoz Kajdic, Vertti Tarvus, Andreas Johlander, Markku Alho, Thiago Brito, Mojtaba Akhavan-Tafti, Maxime Dubart, Urs Ganse, Maxime Grandin, Tomas Karlsson, Yann Pfau-Kempf, Savvas Raptis, Jonas Suni, and Minna Palmroth

The foreshock is a region of space in front of the Earth's bow shock, extending along the interplanetary magnetic field. It is permeated by ions and electrons reflected at the shock, low-frequency waves, and various plasma transients. The ion foreshock is dominated by a number of proton populations such as field-aligned beams, gyrating distributions and diffuse ions, as well as proton-excited waves. As the solar wind can contain a significant fraction of helium, it is of great interest to investigate how alpha-particles (He2+) are reflected into forming their own foreshock. We investigate the extent of the helium foreshock in relation to foreshock ultra-low frequency waves and protons using Vlasiator, a global hybrid-Vlasov simulation. We confirm a number of historical spacecraft observations at the foreshock regions associated with field-aligned beams, gyrating ion distributions, and specularly reflected particles, performing the first numerical global survey of the helium foreshock. We present wavelet analysis at multiple positions within the foreshock and evaluate the dynamics of gyrating ion populations in response to the transverse and compressive wave components. We also present Magnetosphere Multiscale (MMS) spacecraft crossings of the foreshock edge and compare Hot Plasma Composition Analyzer (HPCA) measurements of energetic ions with our simulation data, showing the variability of the foreshock edge suprathermal ion profiles.

How to cite: Battarbee, M., Blanco-Cano, X., Turc, L., Kajdic, P., Tarvus, V., Johlander, A., Alho, M., Brito, T., Akhavan-Tafti, M., Dubart, M., Ganse, U., Grandin, M., Karlsson, T., Pfau-Kempf, Y., Raptis, S., Suni, J., and Palmroth, M.: Helium in the Earth's foreshock: a global Vlasiator survey, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13572, https://doi.org/10.5194/egusphere-egu2020-13572, 2020.

D2953 |
Gérard M. Chanteur

When a shock is moving through a cluster of spacecraft, the normal N to the shock and the velocity of the shock along N can be determined from the crossing times of the different spacecraft assuming that the shock is planar and moves without deformation or rotation during the time interval of the encounter. For a cluster of four spacecraft there are six pairs of spacecraft, each one giving raise to a scalar equation relating the vector position R from the first to the second spacecraft, the normal vector N and the time lag Dt : R.N=VDt. This over-determined system of six equations is solved by computing the pseudo inverse of the matrix M acting on the normal vector on the lhs of the equation. Thus the system is modified by attributing a priori a positive weight to each equation (wj, j=1 to 6) the sum being constrained to 1. Then a statistical ensemble of 6-uplets (wj, j=1 to 6) is built ; for each element of this ensemble we compute the condition number of matrix M and we look for the 6-uplet giving the lowest condition number. This procedure warrants the best accuracy of the pseudo-inverse of M and hence the best estimate of the normal vector N. Adding random perturbations to M and to the time lags allows to estimate the uncertainties on N and V through simulations. This optimized timing method is applied to reanalyze some crossings of the terrestrial bow-shock by CLUSTER and the results are compared to the results obtained by the standard method using the reciprocal vectors defined in the ISSI report SR-008 « Multi-Spacecraft Analysis Methods Revisited » published in 2008. A similar method has been applied to the determination of wave vectors of chorus elements observed by MMS in the inner magntosphere.

How to cite: Chanteur, G. M.: Reanalysis of Some CLUSTER Bow-Shock Crossings With an Optimized Timing Method, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11440, https://doi.org/10.5194/egusphere-egu2020-11440, 2020.

D2954 |
Vertti Tarvus, Lucile Turc, Markus Battarbee, Xochitl Blanco-Cano, Primoz Kajdic, Jonas Suni, Markku Alho, Maxime Dubart, Urs Ganse, Maxime Grandin, Andreas Johlander, Yann Pfau-Kempf, Konstantinos Papadakis, and Minna Palmroth

Upstream of Earth's bow shock lies the foreshock, a region permeated by bow shock-reflected electrons and ions propagating against the incoming solar wind. The interaction between the reflected ions and the solar wind leads to instabilities, which generate Ultra Low Frequency (ULF) waves in the foreshock. Another feature of the foreshock are various propagating transient structures. A particular type of transients are foreshock cavitons, which are characterized as simultaneous depressions of plasma density and magnetic field bounded by edges where these parameters are enhanced.
    Cavitons are proposed to form as a consequence of the non-linear evolution of two ULF wave types. They are carried by the solar wind towards the shock, but have been found to propagate sunward in the solar wind rest frame. Studies have shown that cavitons can accumulate reflected suprathermal ions inside them as they approach the bow shock, causing significant heating and bulk flow deflection in their interiors. These signatures resemble those of Hot Flow Anomalies (HFAs), transients which are associated with interplanetary magnetic field (IMF) discontinuities interacting with the bow shock. As the evolution of cavitons is independent of IMF discontinuities, the hot, evolved transients are classified as spontaneous HFAs (SHFAs). SHFAs arriving to the shock have been found to cause perturbations to the shock surface and the magnetosheath downstream of it.
    In this work, a numerical statistical study of cavitons and SHFAs is conducted with Vlasiator, a global hybrid-Vlasov code. Individual transients are tracked, allowing us to examine their formation rate, propagation characteristics and evolution in addition to their physical properties. Our results show that cavitons and SHFAs form in a uniform region near the bow shock, and there is a distinct distance to the shock within which cavitons can become SHFAs. The density and magnetic field depressions inside cavitons appear well correlated, although shallow compared to spacecraft measurements. We find that both transient types propagate sunwards in the solar wind rest frame, agreeing with earlier studies. Our statistical data set allows us to calculate the propagation velocity, which shows a similar value for all tracked transients. Our results also suggest that the velocity has a southward component. 

How to cite: Tarvus, V., Turc, L., Battarbee, M., Blanco-Cano, X., Kajdic, P., Suni, J., Alho, M., Dubart, M., Ganse, U., Grandin, M., Johlander, A., Pfau-Kempf, Y., Papadakis, K., and Palmroth, M.: Statistical study of foreshock transients in a global hybrid-Vlasov magnetospheric simulation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13632, https://doi.org/10.5194/egusphere-egu2020-13632, 2020.

D2955 |
Maria Hamrin, Ramon Lopez, Pauline Dredger, Herbert Gunell, Oleksandr Goncharov, and Timo Pitkänen

At Earth’s bow shock, the supersonic solar wind is slowed down and deflected around the magnetosphere. To many this is "just a bow shock", a simple and quite passive element of solar-terrestrial physics. However, it has recently been realized that the bow shock plays a significantly more important role with currents on the bow shock connecting through the magnetosheath to the magnetospheric current systems. The bow shock current cannot close locally, since the magnetic field compression in the magnetosheath cannot be maintained globally. The bow shock current is inevitably a generator current extracting mechanical energy from the supersonic solar wind, and feeding it to other processes such as acceleration of the magnetosheath flow, local particle acceleration at the bow shock and dissipation in the distant ionosphere. Here we use data from the first dayside season of the Magnetospheric Multiscale (MMS) mission to investigate the generator properties of the terrestrial bow shock. Typically, the main shock ramp shows clear generator properties, but for some of the more turbulent bow shocks, generator properties may also be observed slightly downstream the ramp. This may be due to effects from shock motions and shock nonstationaity and reformation. Moreover, sometimes a weaker load can be seen in the upstream foot region due to local particle acceleration. We also find that the generator capacity of the bow shock decreases with decreasing bow shock angle as well as with increasing upstream plasma beta and solar Mach number. A better understanding of the energy conversion properties of the terrestrial bow shock will be useful also for the understanding of other astrophysical shock currents. The currents must close somewhere and deposit energy somewhere.

How to cite: Hamrin, M., Lopez, R., Dredger, P., Gunell, H., Goncharov, O., and Pitkänen, T.: Energy conversion at the terrestrial bow shock, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5246, https://doi.org/10.5194/egusphere-egu2020-5246, 2020.

D2956 |
Linus Norenius, Maria Hamrin, Oleksandr Goncharov, Herbert Gunell, Tomas Karlsson, Hermann Opgenoorth, and Siung Chong

The study on high speed plasma flows in the Earth’s magnetosheath, or commonly known as jets, has been a popular topic for discussion in recent decades. These jets can often be characterised by increases in the dynamic pressure compared to the background plasma. They can propagate through the magnetosheath and impact the magnetopause, causing indentations and possibly triggering waves on the magnetopause and contribute to energy and mass transfer into the magnetosphere. Previous studies suggest that the effects from these impacts are detectable inside the magnetosphere at geostationary orbit, and even at ground level causing geoeffective responses. Case studies show indications where ground based magnetometers, GMAGs, have observed magnetic pulses as a result of impacting jets. By using data from the MMS mission and GMAGs, we conduct an observational study with a larger set of jets compared to previous works. The geoeffectiveness of these jets will be investigated and the properties of the responses in the GMAG observations will be discussed.

How to cite: Norenius, L., Hamrin, M., Goncharov, O., Gunell, H., Karlsson, T., Opgenoorth, H., and Chong, S.: Geoeffectiveness of Magnetosheath Jets, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7352, https://doi.org/10.5194/egusphere-egu2020-7352, 2020.

D2957 |
Andrey Samsonov and Graziella Branduardi-Raymont

The relation between the solar wind dynamic pressure and magnetopause standoff distance is usually supposed to be RSUB~Pd-1/N. The simple pressure balance condition gives N=6, however N varies in empirical magnetopause models from 4.8 to 7.7. Using several MHD models, we simulate the magnetospheric response to increases in the dynamic pressure by varying separately the solar wind density or the velocity. We obtain different values of N depending on which parameter, density or velocity, has been varied and for which IMF orientation. The changes in the standoff distance are smaller (higher N) for a density increase and greater (smaller N) for a velocity increase for southward IMF. We explain this result by enhancement of the Region 1 current that moves the magnetopause closer to the Earth for a high solar wind velocity. We suggest for developers of new empirical magnetopause models in the future to replace the simple relation between RSUB and Pd with a fixed N by a more complicated relation which would separate inputs in the dynamic pressure from the density and velocity taking into account the IMF orientation.

How to cite: Samsonov, A. and Branduardi-Raymont, G.: Is the relation between the solar wind dynamic pressure and the magnetopause standoff distance so simple?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1498, https://doi.org/10.5194/egusphere-egu2020-1498, 2020.

D2958 |
Egor Yushkov, Anton Artemyev, and Anatoly Petrukovich

We study the current sheet model separating a strong magnetic field area from the intense solar wind. We use the ideal MHD equations for ideas proposed by D. Nickeler and T. Wiegelmann to describe the transition region with plasma flows inclined to the boundary field. We show that balance in this case can be supported by nondiagonal components of modified pressure tensor. We discuss the possible application of the results to a description of the Earth’s night-side magnetopause boundary and study influence of solar wind characteristics on magnetopause current structure. We show problems that follow from ideal mhd-approach and from our assumptions about stationarity of two-dimensional CS on examples of magnetopause crossings by MMS mission. We speculate about further model development to day-side and magnetopause flanks application. This work is supported by the RFBR grant N 18-02-00218.

How to cite: Yushkov, E., Artemyev, A., and Petrukovich, A.: Role of non-diagonal pressure tensor components in balance of magnetopause current sheet, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21093, https://doi.org/10.5194/egusphere-egu2020-21093, 2020.

D2959 |
Yulia Bogdanova, C.-Philippe Escoubet, Robert Fear, Karlheinz Trattner, Jean Berchem, Andrew Fazakerley, and Frederic Pitout

Observations inside the cusp can be used as distant monitoring of the large-scale geometry and properties of the magnetic reconnection at the magnetopause. The recent modelling and observations of the cusp and flux transfer events in the vicinity of the magnetopause show that the reconnection can occur along the X-line extended over many hours of magnetic local time (MLT), comprising sites of both component and anti-parallel reconnection scenarios. Such observations are in contradiction to the statistical DMSP studies showing that the cusp is rather limited in magnetic local time with an average size 2.5 hours of MLT. Moreover, some past observations indicate that the cusp is moving in response to the changes of the IMF By component, suggesting that the cusp is formed due to anti-parallel reconnection along the X-line limited in MLT.

In this presentation we analyse several events of the mid-altitude cusp observations during the Cluster campaign when the satellites cross the cusp mainly along the longitude in a string-of-pearls configuration during an Interplanetary Magnetic Field (IMF) configuration with a stable and dominant IMF By-component. During this particular Cluster orbit it was possible to define the dawn and dusk cusp boundaries and to study plasma parameters inside different parts of the cusp region. The observations will be discussed in terms of the cusp extension, cusp motion, and possible formation of the ‘double’ cusp structures. Finally, we will consider what these observations reveal about the large-scale reconnection geometry at the magnetopause.

How to cite: Bogdanova, Y., Escoubet, C.-P., Fear, R., Trattner, K., Berchem, J., Fazakerley, A., and Pitout, F.: Mid-altitude cusp dynamics and properties during the IMF By dominated intervals, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7443, https://doi.org/10.5194/egusphere-egu2020-7443, 2020.

D2960 |
Robert L. Richard, David Schriver, Jean Berchem, Mostafa El-Alaoui, Giovanni Lapenta, and Raymond J. Walker

Particle velocity distribution functions measured by spacecraft show that suprathermal ion and electron populations are a common feature of Earth’s magnetosphere.  An outstanding question has been to determine the acceleration processes that lead to the formation of these suprathermal particle populations. Very often, it has been challenging to explain the high levels of energy reached by these particles by simply invoking local processes such as magnetic reconnection. In this presentation, we investigate the hypothesis that suprathermal particle populations increase if the acceleration occurs over multiple steps through different acceleration mechanisms at different spatial locations in Earth’s magnetosphere.  For example, particles transported to the magnetotail which have been accelerated first in the dayside reconnection region could be further accelerated in the tail reconnection regions and then gain additional energy through Fermi and/or betatron acceleration as they convected back to the dayside magnetopause. Since local kinetic processes dominate the acceleration of ions and electrons in the magnetosphere, it has been difficult to validate that hypothesis. Multiple reconnection sites and different possible acceleration regions are too distant to be included in a single kinetic simulation and global hybrid simulations cannot describe electron acceleration.  To address this research problem we leverage our simulation capabilities by combining three different simulation techniques: global magnetohydrodynamic (MHD) simulations, large-scale kinetic (LSK) particle tracing simulations, and large-scale particle in cell (PIC) simulations.  First, we carry out an MHD simulation driven by upstream solar wind and interplanetary magnetic field conditions for a specific time interval featuring active magnetospheric reconnection.  Then we use an implicit PIC simulation of dayside reconnection with initial and boundary conditions from the MHD simulation.  Next, we follow suprathermal particles from the PIC simulation globally through the MHD fields using LSK to assess their transport into the magnetotail. A final step is to perform a PIC simulation embedded in the MHD simulation of magnetotail process including the suprathermal particles arriving from the dayside as determined from the LSK simulation.  Preliminary results indicate that particles energized by dayside reconnection are more likely to reach the magnetotail reconnection region. In addition, the development of enhanced high-energy tails in the particle distributions is promoted by previous energization steps during particle transport to the magnetotail reconnection region.

How to cite: Richard, R. L., Schriver, D., Berchem, J., El-Alaoui, M., Lapenta, G., and Walker, R. J.: Particle Acceleration in Earth’s Global Magnetosphere: a Multiple Step Process, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5823, https://doi.org/10.5194/egusphere-egu2020-5823, 2020.

D2961 |
Mostafa El-ALaoui, Jean Berchem, Robert L. Richard, David Schriver, Giovanni Lapenta, and Raymond J. Walker

An outstanding problem of magnetospheric physics is to determine the energization of particles transported from the nightside to the dayside. To address this research problem, we leverage our simulation capabilities by combining three different simulation techniques: global magnetohydrodynamic (MHD) simulations, large-scale kinetic (LSK) particle tracing simulations, and large-scale particle in cell (PIC) simulations. First, we model a magnetotail reconnection event using an iPic3D simulation with initial and boundary conditions given by a global MHD simulation. The iPic3D simulation system includes the region of fast outflows emanating from the reconnection site that drives the formation of dipolarization fronts.Then, we follow millions of test particles that exit the iPic3D system using the electromagnetic fields from the MHD simulation as they convect to the dayside and quantify the different acceleration and transport mechanisms.

How to cite: El-ALaoui, M., Berchem, J., Richard, R. L., Schriver, D., Lapenta, G., and Walker, R. J.: Particle Acceleration and Transport in the Magnetotail, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6210, https://doi.org/10.5194/egusphere-egu2020-6210, 2020.

D2962 |
Varvara Andreeva, Sergey Apatenkov, Evgeny Gordeev, Noora Partamies, and Kirsti Kauristie

Omega bands are curved aurora forms, which appear as rows of inverted Greek letter Ω drifting eastward and may result in substantial magnetic field variations on the ground. Since they were reported for the first time more than 50 years ago, their ionospheric signatures were thoroughly studied to the present moment. In contrast, magnetospheric processes resulting in the omega-bands generation are poorly understood, mostly due to a small number of conjugated spacecraft observations. Therefore, the only possibility to statistically study magnetospheric features of the omega bands is to use different models.

The goal of the present work is to find a characteristic magnetic field configuration corresponding to this type of aurora. We used the list of omega bands (Partamies et al., 2017), observed in the Fennoscandian Lapland in the period 1997-2007, the MIRACLE all-sky camera data, and new empirical magnetic field model (Tsyganenko and Andreeva, 2016) to identify the magnetospheric equatorial location of the observed omega structures. This work presents the most extensive statistical study of the omega bands projections; in previous papers only a case-study mapping based on few events was described. We found that for 90% of the omega bands aurora its possible source is located on the radial distances from the Earth 6-13 Re in the morning sector (2-4 h MLT), with the average position at R=8 Re and 3 MLT. We also estimated a minimal life-time of the omega bands source in the magnetosphere. This study has been funded by the Russian Science Foundation Grant 19-77-10016.

Partamies, N., Weygand, J. M., and Juusola, L.: Statistical study of auroral omega bands, Ann. Geophys., 35, 1069–1083, https://doi.org/10.5194/angeo-35-1069-2017, 2017.
Tsyganenko, N. A., and V. A. Andreeva (2016), An empirical RBF model of the magnetosphere parameterized by interplanetary and ground-based drivers, J. Geophys. Res. Space Physics, 121, doi:10.1002/2016JA023217.

How to cite: Andreeva, V., Apatenkov, S., Gordeev, E., Partamies, N., and Kauristie, K.: Statistical magnetospheric location of auroral omega bands obtained by empirical magnetic field models, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9851, https://doi.org/10.5194/egusphere-egu2020-9851, 2020.

D2963 |
Guoqiang Wang, Tielong Zhang, Mingyu Wu, Daniel Schmid, Yufei Hao, Zonghao Pan, and Martin Volwerk

Currents are believed to exist in mirror mode structures and to be self-consistent with the magnetic field depression. Here, we investigate a train of mirror mode structures in the terrestrial plasma sheet on 11 August 2017 measured by the Magnetospheric Multiscale mission. We find that bipolar current densities exist in the cross-section of two hole-like mirror mode structures, referred to as magnetic dips. The bipolar current in the magnetic dip with a size of ~2.2 ρi (the ion gyro radius) is mainly contributed by variations of the electron velocity, which is mainly formed by the magnetic gradient-curvature drift. For another magnetic dip with a size of ~6.6 ρi, the bipolar current is mainly caused by an ion bipolar velocity, which can be explained by the collective behaviors of the ion drift motions. These observations suggest that the electrons and ions play different roles in the formation of currents in magnetic dips with different sizes.

How to cite: Wang, G., Zhang, T., Wu, M., Schmid, D., Hao, Y., Pan, Z., and Volwerk, M.: Roles of electrons and ions in formation of the current in mirror mode structures in the terrestrial plasma sheet: MMS observations, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4003, https://doi.org/10.5194/egusphere-egu2020-4003, 2020.

D2964 |
Alessandro Colonico, Simone Di Matteo, and Umberto Villante

An important aspect of the interaction between the solar wind (SW) and the Earth’s magnetosphere concerns the possible relationship between SW and magnetospheric fluctuations under different SW conditions. In recent investigations (Di Matteo and Villante, 2017,2018) we revealed the critical role of the analytical methods and the spectral analysis techniques in the identification of fluctuations between ≈1-5 mHz in the SW parameters as well as in the magnetospheric field measurements at the geostationary orbit and developed a new approach, based on the joint use of the Welch and the Multitaper methods, for a more robust identification of these oscillations in both regions. Here, we extend the analysis to ground measurements, analyzing 22 years of magnetic field measurements along the H and D components at low latitude (L’Aquila, Italy, λ≈36.3°, L≈1.6). We found that, in general, the much steeper spectrum of the geomagnetic fluctuations with respect to the ones estimated in the SW parameters and magnetospheric field, might deeply influence the identification of real events. We then examined, for the entire period, consecutive two hours intervals through the day during low geomagnetic activity conditions (Dst>-50), and, for each interval, we carefully evaluated the characteristics of the background spectrum. As a matter of fact, in the ≈1-5 mHz frequency range the spectral indices of both components typically range between -3.5 and -2 with a steeper spectrum in the night sector when the fluctuations power is lower. Simulations of red noise representations, with spectral indices similar to the observed ones, combined with the Sq variation show a systematic reduction of the rate of identification of real events up to ≈2 mHz.


Di Matteo, S., and U. Villante, J. Geophys.Res. Space Physics, 122, 4905–4920, doi:10.1002/2017JA023936.

Di Matteo, S., and U. Villante, Journal of Geophysical Research: Space Physics, 123, doi.org/10.1002/2017JA024922.

How to cite: Colonico, A., Di Matteo, S., and Villante, U.: Characterization of the Pc5 frequency range power spectrum at low latitude in 22 years of geomagnetic field observations., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4516, https://doi.org/10.5194/egusphere-egu2020-4516, 2020.

D2965 |
Elena Vernova, Natalia Ptitsyna, Olga Danilova, and Marta Tyasto

The geomagnetic cutoff rigidity R (momentum per unit charge) is the threshold rigidity below which the particle flux becomes zero due to geomagnetic shielding. The properties of the geomagnetic screen vary greatly during magnetic storms, depending on the dynamic interaction of the solar wind (SW) magnetic fields with the magnetospheric fields and currents. The correlation between the variations of geomagnetic cutoff rigidity ΔR and interplanetary parameters and geomagnetic activity indexes during various phases of the superstorm on November 7 – 8, 2004 has been calculated. On the scale of the entire storm the most geoeffеctive parameters were Dst, Kp, and SW speed, while other parameters, including total interplanetary magnetic field B and Bz component, were effective at different phases of the storm.

How to cite: Vernova, E., Ptitsyna, N., Danilova, O., and Tyasto, M.: Correlation between the variations of cosmic ray geomagnetic thresholds and interplanetary parameters during various phases of solar disturbance in November 2004, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9971, https://doi.org/10.5194/egusphere-egu2020-9971, 2020.

D2966 |
Wei Chu, Song Xu, ZhenXia Zhang, Jianping Huang, Zhima Zeren, and Xuhui Shen

Based on the observation data collected by the Energetic Particles Detector Package(HEPP) on board CSES satellite during the period of 2018 and 2019.We analyzed the characterizes of pitch angle spectrum of energetic electron precipitated caused by NWC. Our analysis revealed in details the transient properties of the space electrons induced by the man-made VLF wave emitted by the transmitter at NWC.The center location of the NWC electron flux locates in the north hemisphere other than in the south hemisphere during both quiet and disturbance period which is surprising.And the central location of NWC electron belt move westwards during the geomagnetic storm.The pitch angle distributions of the precipitation electron have the maximum flux at about 60-70 degree other than at 90 degree.The pitch angle distributions presented here are examined for evidence of the transportation mechanism especially for the electron loss mechanism.


How to cite: Chu, W., Xu, S., Zhang, Z., Huang, J., Zeren, Z., and Shen, X.: Study on the variation of energetic particle pitch angle caused by NWC VLF transmitter, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4488, https://doi.org/10.5194/egusphere-egu2020-4488, 2020.