ST2.4

Various types of plasma waves play key roles in magnetospheric physics in contexts ranging from the magnetosphere and its boundary layers to planetary bow shocks and foreshocks.  Due to limited available spacecraft measurements, the waves are often assumed to be plane waves that extend to infinity in all directions. A good example is the Earth's ion foreshock where intrinsically right-hand circularly polarized magnetosonic modes are generated by a fast ion beam. Many prior studies of these waves assume no variation of important physical quantities in the direction perpendicular to wave propagation. We show that Magnetic Gauss's Law implies that this assumption must be violated near the edge of the wave domain. The resulting false signature in the standard Magnetic Gauss's Law calculation of the wave vector orientation may be used to detect the domain edge. We demonstrate this new edge detection method in a simple wave model, a 2-D hybrid Vlasov simulation conducted using the Vlasiator code, and ARTEMIS spacecraft observations. In both the simulation and the spacecraft observations, this new signature is shown to correlate well with a determination of the foreshock edge based on the properties of the fast ion beam.  As the plane wave assumption is widely used in space physics data analysis techniques such as minimum variance analysis, these results may stimulate a reexamination of this assumption in other magnetospheric physics contexts.

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

How to cite: Dorfman, S., Zhang, K., Turc, L., and Ganse, U.: Detecting the edges of Earth's ion foreshock using Magnetic Gauss's Law, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10698, https://doi.org/10.5194/egusphere-egu22-10698, 2022.

Large-amplitude ULF waves are usually observed in the foreshock region ahead of quasi-parallel shocks and their generation is driven by the backstreaming ions. In the early phase of the wave growth, the waves are growing with time and traveling in space simultaneously. Therefore, it is very difficult to observe the wave growth properly using single-point measurements such as single spacecraft observations, because the spatial and temporal variations cannot be decoupled. This has also brought difficulties into understanding the detailed physical connection between the foreshock ion properties and the wave properties. In comparison, it is more straightforward to study this problem in global simulations, as simulation results are available everywhere in the foreshock at all times. Here we perform detailed analysis of the ULF wave growth and its relationship with the ion distribution using a Vlasiator simulation (a hybrid-Vlasov code). We calculate the phase speed of the ULF waves and observe the wave growth in the wave frame continuously. We show that the growth rate of the ULF waves decreases with time due to the decrease in beam velocity and the scatter of the ion distribution. And we compare the calculated growth rate with the dispersion relation solved by LEOPARD (a dispersion solver with arbitrary ion distribution input) based on the corresponding ion distribution obtained from the simulation results, and we will discuss the related physical mechanisms such as the ion-ion beam instability when the wave growth can be explained by ion distribution and discuss possible reasons when there is any discrepancy.

How to cite: Zhang, K., Dorfman, S., Turc, L., Ganse, U., Shi, C., and Palmroth, M.: The early-phase growth of ULF waves in the ion foreshock observed in a hybrid-Vlasov simulation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6812, https://doi.org/10.5194/egusphere-egu22-6812, 2022.

We present a large statistical study of the ultra-low frequency (ULF) waves in the terrestrial foreshock. These waves are excited in the upstream region by energetic ions streaming along the solar wind magnetic field lines connected to the bow shock. Although these waves propagate upstream and grow in the solar wind frame, they are blown down by the solar wind flow and thus their amplitudes would grow toward the bow shock. In our previous study based on ARTEMIS observations, we demonstrated that the statistically determined growth rate is positive but also the cases of a wave decay are frequently observed. We have shown that even if a possible influence of the Moon and its wake is excluded, the growth rate is decreased by non-linear effects leading to a saturation of the wave amplitude. To eliminate this problem, we have selected intervals allowing identification of an initial stage of wave amplitude growth (either in spatial or temporal sense). Our study revealed that the growth rate depends on the wave type being larger for compressive variations of the magnetic field strength and plasma density than for variations of magnetic field components. The analogous study of velocity fluctuations leads to smaller growth rates and we discuss possible causes of this disagreement.

How to cite: Salohub, A., Safrankova, J., and Nemecek, Z.: The foreshock wave activity under quasi radial magnetic field in lunar distances: Statistical study, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1360, https://doi.org/10.5194/egusphere-egu22-1360, 2022.

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-second" 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 periods) in the dayside magnetosphere, but how the waves can transmit through the bow shock and across the magnetosheath remains unclear. Global hybrid-Vlasov simulations performed with the Vlasiator model provide us with the global view of foreshock wave transmission across near-Earth space. We find that the foreshock waves act as fast-mode pulses hammering periodically the shock, which impulsively sends perturbations in the downstream at the fast-mode speed. These fast-mode disturbances propagate in the magnetosheath all the way to the magnetopause, where they can further transmit into the dayside magnetosphere. The wave propagation across the bow shock appears to be much more complex than the simple "direct transmission" of the foreshock waves which was inferred in early studies. This is due to the complex two-way interactions between the waves and the shock, including shock reformation. We compare our global simulation results with local 1D simulations, and we show that the wave signatures in the downstream strongly depend on the global properties of the shock-magnetosheath system. This emphasises the importance of carrying out global simulations in this context.

How to cite: Turc, L., Roberts, O., Verscharen, D., Dimmock, A., Kajdic, P., Palmroth, M., Pfau-Kempf, Y., Johlander, A., Dubart, M., Kilpua, E., Soucek, J., Takahashi, K., Takahashi, N., Battarbee, M., and Ganse, U.: Transmission of foreshock waves through the Earth’s magnetosheath, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7655, https://doi.org/10.5194/egusphere-egu22-7655, 2022.

Plasma structures with enhanced density or dynamic pressure, also known as jets or plasmoids, are often observed in Earth’s magnetosheath. Early studies of jets in the magnetosheath have indicated that the jet formation is closely related to processes in the foreshock region. Based on the magnetic field changes, Karlsson et al. (2015) divided the plasmoids into two distinct groups. They observed numbers of “diamagnetic” plasmoids in the foreshock region and suggested that Short Large Amplitude Magnetic Structures (SLAMS) could be a source of both plasmoid types in the magnetosheath. Using measurements by the Magnetospheric Multiscale (MMS) spacecraft we present a statistical analysis of foreshock compressive structures with significantly enhanced density and dynamic pressure. Based on our statistical analysis and previous studies, we discuss features of those structures, their properties, occurrence, evolution, and relation to the magnetosheath jets and plasmoids.

How to cite: Xirogiannopoulou, N., Goncharov, O., Safrankova, J., Nemecek, Z., and Salohub, A.: Foreshock compressive structures and their relations to jet-like events in the magnetosheath, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1745, https://doi.org/10.5194/egusphere-egu22-1745, 2022.

Magnetosheath jets are transient localized structures of enhanced dynamic pressure observed downstream of the Earth’s bow shock. They may exhibit an increase of velocity reaching solar wind levels, while their density is typically much higher than typical magnetosheath and solar wind values. Jets have been associated to several magnetospheric effects such as, magnetopause reconnection, excitations of surface eigenmodes and even direct plasma penetration in the magnetosphere. While their exact origin is unknown, many mechanisms have been proposed. One of the most prominent explanations involves the interaction of solar wind with local inclinations of the bow shock (ripples) while others include solar wind discontinuities, and foreshock structures.

In this work, by using Magnetosphere Multiscale (MMS) we show in-situ observations of a super-magnetosonic magnetosheath jet being generated as a direct result of the bow shock reformation cycle. The observed jet origin appears to be the result of the dynamical evolution of the shock and the emergence of a spatially de-attached compressive magnetic structure that acts as a local shock front. Due to this, the solar wind particles are effectively transferred downstream without experiencing a strong interaction with the shock, which allows compressed high velocity plasma to be observed downstream of the bow shock.

The proposed mechanism does not require external phenomena (e.g., solar wind discontinuities) or specific configuration of the bow shock (e.g., ripples) to take place. On the contrary, it allows the magnetosheath jet phenomenon to directly originate from the dynamical evolution of the quasi-parallel collisionless shock.

How to cite: Raptis, S., Karlsson, T., Vaivads, A., Pollock, C., Plaschke, F., Johlander, A., Trollvik, H., and Lindqvist, P.-A.: High-speed Magnetosheath Jet Generation due to Shock Reformation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2750, https://doi.org/10.5194/egusphere-egu22-2750, 2022.

Localized enhancements in dynamic pressure observed in the Earth’s magnetosheath (EMS) have been studied since 20 years ago. These structures known as jets can propagate through the EMS transporting mass, momentum and energy being able to reach and perturb the Earth’s magnetopause.
Large scale solar wind (SW) structures called Coronal Mass Ejections (CMEs) travel through the interplanetary medium and depending on their direction they may impact the Earth. How the different SW conditions triggered by the CMEs (upstream side – shock/sheath – magnetic ejecta) change the production of jets in the EMS is a topic that is just beginning to be explored.
In this case study we characterize jets observed by THEMIS A, E and D during a CME passage. We find clear differences in number and size between the jets associated with the different CME regions arriving at the EMS. Comparing WIND and THEMIS data we discuss how these differences are associated with the SW conditions and with different jet generation mechanisms.

How to cite: Preisser, L., Plaschke, F., Koller, F., Temmer, M., and Roberts, O.: Magnetosheath jets during an CME passage: A case study, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11999, https://doi.org/10.5194/egusphere-egu22-11999, 2022.

Magnetosheath jets are dynamic pressure enhancements frequently observed in the Earth’s magnetosheath. They are significant coupling elements between the solar wind and the magnetosphere of the Earth and they can be geoeffective. Jets travel anti-sunward through the magnetosheath and can impact the magnetopause. The generation of these jets is generally linked to processes at the quasi-parallel bow shock and the foreshock. We analyzed how the appearance of these jets is linked to large-scale solar wind (SW) structures, in particular coronal mass ejections (CMEs) and stream interaction regions (SIRs) and their associated high speed streams (HSSs). In our statistical analysis, we use magnetosheath jets detected by the THEMIS spacecraft between 2008 to 2020. We found that the number of detected jets is lower during the passing of CMEs. Significantly more jets are observed during SIRs and HSSs. We analyze the difference in conditions during each SW structure and compare them to the SW conditions measured during the detection of jets. We focus on SW Alfvénic Mach number and IMF cone angle, which affect the presence of the foreshock and the position of the quasi-parallel shock front. We find that jets are unlikely to appear during a mix of low Alfvénic Mach numbers and high cone angles, which are SW conditions often found during CMEs and their associated sheaths.

How to cite: Koller, F., Plaschke, F., Preisser, L., Temmer, M., and Roberts, O. W.: Solar wind conditions suppressing the production of magnetosheath jets during CME occurrence, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6521, https://doi.org/10.5194/egusphere-egu22-6521, 2022.

Whistler waves, right-hand polarized waves with frequencies below the electron cyclotron frequency, are common in many space plasma regions such as the Earth’s magnetosheath. They can be generated by electron temperature anisotropy, in which case the instability grows through cyclotron resonance. A common way to determine the stability of an electron distribution function is to compare the parallel and perpendicular temperature (with respect to the background magnetic field) to stability thresholds. However, such an approach based on the moments of the distribution function can potentially leave out some properties of the distribution which are important for wave generation.

In this work, we investigate the features of the electron distribution functions measured by MMS in the turbulent magnetosheath downstream of a quasi-parallel shock. We show that even though statistically whistler waves tend to occur close to the regions where the stability threshold is exceeded, they are also observed in regions predicted to be stable to wave generation. For such waves we observe that the electron pitch angle distribution often has the so-called butterfly shape (with minima in both the parallel and perpendicular directions) and is located in magnetic field minima. Using a linear numerical dispersion solver (WHAMP), we show that the butterfly distribution is unstable to whistler wave generation even though the instability threshold based on the associated moments is not exceeded. Comparison between the numerical results and waves measured by the MMS spacecraft indicate that the observed whistler waves are generated by the butterfly distribution. This phenomenon has previously been observed in mirror modes and large scale magnetic holes. Our findings show that it also occurs on smaller scales (~1 ion inertial length) in more turbulent environments, such as the quasi-parallel magnetosheath.

How to cite: Svenningsson, I., Yordanova, E., Khotyaintsev, Y., André, M., and Cozzani, G.: Kinetic generation of whistler waves in the turbulent magnetosheath, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5337, https://doi.org/10.5194/egusphere-egu22-5337, 2022.

The process of charge exchange between solar wind highly charged heavy ions and exospheric neutrals produces soft X-rays in geospace. The regions with the strongest emissivity are the magnetosheath and cusps. The Soft X-ray Imager (SXI) on board the forthcoming SMILE mission will measure X-ray emissivity integrated along the line-of-sight. By analyzing 2-D maps of X-ray counts from the SXI, we can extract information about magnetopause shape and position. It has been suggested that the maximum of integrated emissivity is tangent to the magnetopause. We check this assumption using the results of MHD simulations for different points along the SMILE trajectory. We show that this method can be used for finding the magnetopause location if some corrections are applied. We present methods of determining the location of the maximum of integrated emissivity using SXI counts maps for a moderately and strongly compressed magnetosphere.

How to cite: Samsonov, A., Sembay, S., Carter, J., Branduardi-Raymont, G., and Read, A.: Using X-ray imaging to find the magnetopause location, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9036, https://doi.org/10.5194/egusphere-egu22-9036, 2022.

Magnetic reconnection is a fundamental process that is ubiquitous in the universe and allows the conversion of the magnetic field energy into heating and acceleration of plasma. It’s also very important as it is responsible for the dominant transport of plasma, momentum, and energy across the magnetopause from the solar wind into the Earth magnetosphere. Coronal Mass Ejections (CMEs) and Corotating Interaction Regions (CIRs) are the primary large-scale propagating structures and important drivers of unusual space weather disturbances causing magnetospheric activity. The present study reports on a magnetic reconnection event detected by the Magnetospheric Multiscale mission (MMS) on 21 October 2015 around 04:40 UT and related to a large-scale solar wind (SW) perturbation impacting the Earth’s magnetopause. Based on OMNI data, the event impacting the Earth’s magnetosphere is ahead of weak CIR (SW beta=~7 and Alfvénic Mach number~15) where the density of solar wind is about ~20 cm ^-3 (compared with average SW density ~3-10 cm ^-3). Furthermore, the magnetosheath (MSH) density measured by MMS just after the crossing of the magnetopause is about ~95 cm ^-3 (compared with average MSH density ~20 cm ^-3). Reconnection signatures such as ion and electron jets, Hall field, and energy conversion are compared with a “classical” reconnection event observed during quiet solar wind conditions.

How to cite: Baraka, M., Le Contel, O., Canu, P., Alqeeq, S., Akhavan-Tafti, M., Retino, A., Chust, T., Alexandrova, A., and Fontaine, D. and the MMS Team: Study of a dayside magnetopause reconnection event detected by MMS and related to a large-scale solar wind perturbation., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9556, https://doi.org/10.5194/egusphere-egu22-9556, 2022.

Occasionally, the auroral oval is filled with arcs pointing from the night side towards the cusp. These aurorae are known as cusp-aligned arcs. While there have been some theoretical predictions about their origins, the cause of these arcs remains unknown. For this study, we have identified both cusp-aligned arcs and regular transpolar arcs from DMSP satellite data. We investigate the correlation between the appearance of cusp-aligned arcs and various solar wind parameters, with a focus on IMF B_Z and solar wind velocity. These results are then compared to the occurrence of regular transpolar arcs with respect to the same parameters. We see that cusp-aligned arcs appear almost exclusively when the IMF is northward for a long period of time, contrary to regular transpolar arcs which can have a varying, but typically northward on average, IMF. This result is in agreement with previous studies. No clear correlation between the solar wind velocity and cusp-aligned arc occurrence frequency can be seen. The results indicate that cusp-aligned arcs might be caused by Kelvin-Helmholtz instabilities at the flanks, as has been previously suggested. We also discuss other potential causes and models of cusp-aligned arcs in further detail. Additionally, we investigate the conjugacy of cusp-aligned arcs, based on DMSP data.

How to cite: Thor, S., Kullen, A., and Cai, L.: The IMF BZ Dependence of Cusp-Aligned Arcs, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6554, https://doi.org/10.5194/egusphere-egu22-6554, 2022.

Ion dynamics are controlled by the energy-dependent source, transport, energization, and loss processes. Systematic changes in the ion dynamics are essential to understand the ring current variations in the inner magnetosphere. The Van Allen Probes mission, which orbits near the equatorial plane inside the geosynchronous orbit, has a wide energy coverage with high energy resolution and state-of-the-art ion composition instrumentation. It provides a great opportunity to investigate plasma dynamics. In this talk, I will present some of our recent studies on the ion dynamics of different populations and species as well as the related plasma wave activity during geomagnetic quiet and active times.

How to cite: Yue, C.: Ion dynamics in the inner magnetosphere during Van Allen Probe Era, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-901, https://doi.org/10.5194/egusphere-egu22-901, 2022.

Metallic and silicate ions carry essential information about the evolution of the Earth and near-Earth small bodies. Despite this, there has so far been very little focus on ions with atomic masses higher than oxygen in the terrestrial magnetosphere. In this presentation, we report on abundances and  properties of energetic ions with masses corresponding to that of silicon (Si) and iron (Fe) in Earth's geospace.  The results are based on a newly derived data product from the Research with Adaptive Particle Imaging Detectors (RAPID) on Cluster. We find traces of both Si and Fe in all of the regions covered by the spacecraft, with the highest occurrence rates and highest intensities in the inner magnetosphere. We also find that the Fe and Si abundances are modulated by solar activity. During solar maximum, the probability of observing Fe and Si in geospace increases significantly. On the other hand, we find little or no direct correlation between geomagnetic activity and Si and Fe abundance in the magnetosphere. Both Si and Fe in the Earth's magnetosphere are inferred to be primarily of solar wind origin, as indicated by correlations with heavy ion observations from the ACE spacecraft at L1. Sputtering off the Moon is another possible source of the observed heavy ions.

How to cite: Haaland, S., Daly, P. W., Vilenius, E., and Krcelic, P.: Heavy Metal and Rock in Space: Cluster RAPID Observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3519, https://doi.org/10.5194/egusphere-egu22-3519, 2022.

Molecular and metallic ions are vastly unexplored in near-Earth space because only a few terrestrial missions have been equipped with dedicated instrumentation to separate these molecular and metallic ions, within only a limited energy range (cold ions of < 50 eV and energetic ions of ~100 keV).  Nevertheless, existing data from past and on-going missions including those not designed for the required mass separation are capable of detecting many of these ions with available tools, although severe limitations exist (sensitivity and energy range in addition to mass resolution and mass range).  By combining these patchy and incomplete data, we found several features that indicate sources of these heavy ions.
(1) Combination of Kaguya and Cluster/RAPID during high flux events of solar wind heavy ions suggests that the Moon can be a substantial source for low charge-state metallic ions in the magnetosphere when the Moon is located upstream of the Earth.  This interpretation is consistent with Geotail/STICS statistics of increased flux of low charge-state heavy ions near new-Moon for medium activity (Kp=2-4).
(2) The major route of molecular ion supply (<10 keV) to the inner magnetosphere can be via low-latitude (< 60° invariant latitude, according to e-POP/IRMS) in addition to the cusp (according to Cluster/CIS and Akebono/SMS) during high outflow flux period.  This indicates extraordinary upward convection (or ion flow) at the sub-auroral region.
(3) A case study of lidar data during high flux events of solar wind heavy ions suggests that upward expansion of Na signal can be associated with molecular ion escape to the magnetosphere that is also observed by Cluster/RAPID and e-POP/IRM, although this expansion can be related to a major magnetic storm rather than solar wind event.

How to cite: Yamauchi, M., Dandouras, I., Mann, I., Haaland, S., Würz, P., Plane, J., Kastinen, D., Gunnarsdottir, T., Yau, A., Kistler, L., Hamilton, D., Christon, S., Saito, Y., Watanabe, S., and Nozawa, S.: Molecular and metalic ions in the magnetosphere: ISSI team preliminary results, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1297, https://doi.org/10.5194/egusphere-egu22-1297, 2022.

The Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) has revolutionized the way in which we can study the electrical current systems present over the poles of Earth. With high cadence measurements taken in both hemispheres, the data has proven invaluable in developing our understanding of the current systems that couple the magnetosphere and ionosphere and how they change in response to space weather. By employing the AMPERE data set, we aim to offer new insights into the complex and dynamic region 1 and region 2 current systems as they respond to the impact of solar wind disturbances on the magnetosphere and the driving of geomagnetic storms.

We investigate the relationship between the hemispherically-integrated current flowing into or out of each pole and upstream solar wind parameters to understand how these currents are driven.  As expected, current magnitude increases with increasing interplanetary magnetic field strength and solar wind speed.  A key aim of the analysis is to determine if current magnitude saturates under strongly driven conditions, in the same way that the cross-polar cap potential is known to saturate.  We present preliminary results, indicating a variety of behaviours at high driving, and discuss these in terms of theories of solar wind-magnetosphere coupling.

How to cite: Fleetham, A., Milan, S., Imber, S., and Anderson, B.: AMPERE and The Electric Current of the Geomagnetic Storm, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1800, https://doi.org/10.5194/egusphere-egu22-1800, 2022.

The polar cap potential, a measure of the magnetosphere's response to the solar wind, levels off during high solar wind electric field values. Several explanations have been proposed for this saturation effect, but there has been no consensus. We show that the saturation may merely be a perception created by uncertainty in the solar wind measurements and its propagation to the polar cap. Correcting this uncertainty reveals a true response that is linear across the full range of the solar wind electric field values. These findings indicate that extreme space weather events can elicit a larger impact on Earth than we'd expect if the polar cap potential were to saturate.

How to cite: Sivadas, N., Sibeck, D., Subramanyan, V., Walach, M.-T., Murphy, K., and Halford, A.: Uncertainty in solar wind propagation may explain polar cap potential saturation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6366, https://doi.org/10.5194/egusphere-egu22-6366, 2022.

The strong growth of the space sector along with the use of smaller satellites, for example Cubesats, has fueled the rising implementation of satellite constellations. Not only in commercial spaceflight small satellite constellations are used frequently - there also have been ideas put forward for scientific missions using constellations exceeding the 4 spacecraft constellations previously used for in-situ multi-point measurements in space plasma physics (e.g. CLUSTER or MMS). Thus, there is a need to expand current analysis techniques of those multi-point measurements to more than 4 spacecraft and characterize the benefits of a larger number of satellites. Such an analysis technique is the wave telescope, e.g. introduced in Motschmann et al., 1996. The wave telescope allows to use e.g. magnetic field data from different points in space (the different spacecraft) to estimate a spatial fourier transform and with that is able to detect multiple waves. Thus, using a confined time interval, the frequency and wave vector of several different waves can be detected with high precision. Since its introduction, the wave telescope has been successfully applied for detection of waves in in-situ magnetic field data from Earth's magnetospheric environment. Using artificial data of magnetic plane waves in simulations, we revisit the limitations of the wave telescope for satellite numbers of 4 or less and explore the quality of detection for satellite configurations of 5 and more spacecraft. We present structured analysis of the spatial analysis limit from 1D upwards, named the nyquist wavenumber or wave vector (analogous to the nyquist frequency in the frequency domain). Additionally, we show that the wave telescope suffers from so called spatial blindness when the chosen satellite configuration is not moving and non-random phase plane waves at the same frequency are present. This blindness reduces the possible number of waves detected to no more than one.

How to cite: Schulz, L., Glassmeier, K.-H., Plaschke, F., and Motschmann, U.: Revisiting the wave telescope for larger numbers of spacecraft, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4018, https://doi.org/10.5194/egusphere-egu22-4018, 2022.

Poloidal–toroidal magnetic field decomposition is a useful application of the Mie representation for the reconstruction of Mercury‘s internal magnetic field. In addition, the decomposition method enables us to determine the current density observationally and unambiguously in the local region of magnetic field measurement. The application and the limits of the decomposition method are tested against the Mercury magnetic field simulation in view of BepiColombo‘s arrival at Mercury in 2025. The simulated magnetic field data are evaluated along the planned Mercury Planetary Orbiter (MPO) trajectories and the current system that is crossed by the spacecraft is extracted from the magnetic field measurements. Afterwards, the resulting currents are classified in terms of the established current system in the vicinity of Mercury.

Reference

• Toepfer, S., Narita, Y., Exner, W., Heyner, D., Kolhey, P., Glassmeier, K. ‐H., Motschmann, U. (2021c)  The Mie representation for Mercury’s magnetospheric currents, Earth, Planets and Space 73:204. https://doi.org/10.1186/s40623-021-01536-8

• Toepfer, S., Narita, Y., Glassmeier, K.-H., Heyner, D., Kolhey, P., Motschmann, U., Langlais, B. (2021a) The Mie representation for Mercury’s magnetic field, Earth Planets Space 73:65. https://doi.org/10.1186/s40623-021-01386-4

How to cite: Töpfer, S., Narita, Y., Heyner, D., Kolhey, P., Glassmeier, K.-H., and Motschmann, U.: The Mie representation for Mercury‘s magnetospheric currents, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2575, https://doi.org/10.5194/egusphere-egu22-2575, 2022.

In the present work, we consider 49 dipolarization fronts (DF) detected by the Magnetospheric Multiscale (MMS) mission on 2017, near the Earth’s magnetotail equator (Bx<5nT). Criteria for selecting DF using an AIDApy routine are based on difference of maximum and minimum values computed with a 306 s sliding window. They request a Bz increase, an ion velocity increase and a density decrease. This first automatic selection is then ajusted manually with the following criteria : Bz increase larger than 5 nT, ion velocity larger than 150 km/s, density decrease and both ion and electron temperature increases. All these events belong to the most common category (A) defined by Schmid et al., 2015 in term of density decrease and temperature increase at the DF. However, based on a superposed epoch analysis of DF basic properties (magnetic field, density, velocity, ...) we distinguish two subcategories of events depending on the shape of the DF. The first subcategory (55.1%) corresponds to a slow decrease of the magnetic field after the DF and is associated with smaller ion velocity and hotter plasma. The second subcategory (44.9%) has the same time scale for the rising and the falling of the magnetic field (a bump) associated with a decrease of ion and electron pressures and faster velocity as shown in Alqeeq et al. 2021. For both categories we found that ions are mostly decoupled from the magnetic field by the Hall fields. The electron pressure gradient term is also contributing to the ion decoupling and likely responsible for an electron decoupling at DF. We also analyzed the energy conversion process. For the first subcategory we found that the energy in the spacecraft frame is transferred from the electromagnetic field to the plasma (J·E>0) ahead or at the DF. For the second subcategory, we found the same behavior ahead or at the DF whereas it is the opposite (J·E<0) behind the front. In the fluid frame, we found that the energy is mostly transferred from the plasma to the electromagnetic field (J·E ′ <0) ahead or at the DF for both subcategories but energy dissipation (J·E ′ >0) only occurs behind the front for the second subcategory. The possible origin of these two subcategories is discussed.

How to cite: Alqeeq, S., Le Contel, O., Canu, P., Retinò, A., Breuillard, H., Chust, T., Alexandrova, A., Mirioni, L., Khotyaintsev, Y., Nakamura, R., Wilder, F., Wei, H., Fischer, D., Gershman, D., Burch, J., Torbert, R., Giles, B., Fuselier, S., Ergun, R., and Lindqvist, P. A. and the MMS Team: A statistical study of dipolarization fronts observed by MMS, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9532, https://doi.org/10.5194/egusphere-egu22-9532, 2022.

The compressible electron magnetohydrodynamics (EMHD) Grad–Shafranov (GS) reconstruction technique is applied to recover a magnetic reconnection electron diffusion region (EDR) immersed in a flux‐rope type dipolarization front observed by the Magnetospheric Multiscale (MMS) mission on 8 September 2018 at nearly 14:51:30 UT. An event was reported in the study of Marshall et al. (JGR, 2020). EMHD GS reconstruction confirms mainly the results of the cited study. Particularly, MMS1 is found to cross the very center of EDR at the initial steady-state stage. The reconstruction results allow also the suggestion that the reported X-line and EDR were not single ones, but rather the chain of X-lines (two at least) separated in north-south direction for about 10 d_e could exist.

How to cite: Korovinskiy, D., Panov, E., Nakamura, R., and Hosner, M.: EMHD Grad–Shafranov reconstruction of the electron diffusion region within a flux rope, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4579, https://doi.org/10.5194/egusphere-egu22-4579, 2022.

The Dipolarization Front (DF), which is a sharp increase of the northward magnetic field component, accompanied by fast earthward-moving plasma flows, is a well known phenomenon in the Earth's Magnetotail. Plasma characteristics also change at the front, from colder and denser ahead of the front to a hotter and more diluted plasma at the trailing side. The DF is therefore considered to be the boundary between ambient plasma and the hotter reconnection outflow jets. The DF can be the host of several energy conversion processes between plasma particles and waves e.g. due to various instabilities. A recent statistical study by Hosner et al. PoP 2022 showed that all of the studied DFs are accompanied by enhanced wave activity around the lower hybrid frequency, suggesting the high occurrence of the Lower-Hybrid Drift instability (LHDI) at DFs. In the present study we investigate the evolution of the energy conversion process in a flux rope type DF, for which an electron-diffusion region was reported (Marshall et al. JGR 2020). We first examine the wave characteristics and LHDI signatures to compare and to contrast flux rope and non-flux rope type DFs. Secondly, we apply a magnetic field reconstruction technique (Denton et al. JGR 2020) to this event using MMS data, to reconstruct the changes of the local magnetic field structures of the flux rope and temporal/spatial evolution of the energy conversion processes within the DF.

How to cite: Hosner, M., Nakamura, R., Schmid, D., Nakamura, T., Panov, E., and Korovinskiy, D.: Investigation of the evolution of energy conversion processes at an EDR-accompanied dipolarization front, using polynomial magnetic field reconstruction techniques, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5853, https://doi.org/10.5194/egusphere-egu22-5853, 2022.

We investigate a series of Earthward bursty bulk flows (BBFs) observed by the Magnetospheric Multiscale (MMS) spacecraft in the Earth’s magnetotail (X ~ -24 Re, Y ~ 7 Re, Z ~ 4 Re). At the leading edges of the BBFs, we observe complex magnetic field structures. In particular, we focus on one which presents a chain of small scale (~0.5 Re) dipolarizations, and another with a large scale (~3.5 Re) dipolarization. Although the two structures have different scales, both of these structures are associated with flux increases of supra-thermal ions (Ki > 100 keV). We investigate the ion acceleration mechanism and its dependence on the mass and charge state. We show that the ions with gyroradii smaller than the scale of the structure are accelerated by the ion bulk flow. We show that whereas in the small-scale structure, ions with gyroradii comparable with the scale of the structure undergo resonance acceleration, the acceleration in the larger-scale structure is more likely due to a spatially limited electric field. In both cases, we discuss the adiabaticity of the acceleration mechanism.

How to cite: Richard, L., Khotyaintsev, Y. V., Graham, D. B., Vaivads, A., Nikoukar, R., Cohen, I. J., Turner, D. L., Fuselier, S. A., Russell, C. T., Giles, B. L., and Lindqvist, P.-A.: Ion Acceleration at Magnetotail Turbulent Plasma Jet Fronts, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4045, https://doi.org/10.5194/egusphere-egu22-4045, 2022.

The near-Earth electron population is largely formed by earthward electron transport from the middle and distant magnetotail. Such transport is associated by electron adiabatic heating by the convection electric field. Although the adiabatic heating models predict formation of strongly anisotropic electron populations, spacecraft observations show that hot electrons are well isotropic in the near-Earth magnetotail. One of the possible isotropisation mechanisms is the electron scattering by magnetic field line curvature in the magnetotail current sheet with the stretched magnetic field line configuration.  In this presentation we show model results of electron transport and curvature scattering for slow magnetosphere convection. Our model combines the canonical theory of the electron guiding center motion and the mapping technique of electron pitch-angle scattering. We show formation of electron spectra typical for the near-Earth magnetotail and estimate the contribution of the curvature scattering to electron losses.

How to cite: Shustov, P., Artemyev, A., and Petrukovich, A.: Electron earthward transport in the Earth magnetotail: adiabatic convection heating and magnetic curvature scattering, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6459, https://doi.org/10.5194/egusphere-egu22-6459, 2022.

In July 2017, the MMS constellation was evolving in the magnetotail with an apogee of 25 Earth radii and an average inter-satellite distance of 10 km (i.e. at electron scales). On 23^rd of July around 16:19 UT, MMS was located at the edge of the current sheet which was in a quasi-static state. Then, MMS suddenly entered in the central plasma sheet and detected the local onset of a small substorm as indicated by the AE index (~400 nT). Fast plasma flows towards the Earth were measured for about 1 hour starting with a period of quasi-steady flow and followed by a series of saw-tooth plasma jets (“bursty bulk flows”). In the present study, we focus on a short sequence related to the crossing of an ion scale current sheet embedded in a fast earthward flow. The current sheet appears to be corrugated and with a significant guide field (BL/BM~0.5). Tailward propagating electrostatic solitary waves are detected just after the magnetic equator crossing and at the edge of the current sheet. We also analyze in detail an electron vortex magnetic hole also detected at the edge of this current sheet and discuss the Ohm’s law and energy conversion processes. We find that the energy dissipation associated with the electron vortex is three times greater (0.15nW/m3) than at the current sheet crossing (0.05nW/m3). Based on estimated statistical weight of these vortices we discuss possible consequences for the energy dissipation associated with fast earthward plasma flows.

How to cite: Le Contel, O., Retino, A., Alexandrova, A., Nakamura, R., Alqeeq, S., Baraka, M., Chust, T., Mirioni, L., Catapano, F., Jacquey, C., Toledo-Redondo, S., Stawarz, J., Goodrich, K., Gershman, D., Fuselier, S., Mukherjee, J., Ahmadi, N., Graham, D., Argall, M. R., and Fischer, D. and the A MMS Team: Multiscale analysis of a current sheet crossing associated with a fast earthward flow during a substorm event detected by MMS, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9481, https://doi.org/10.5194/egusphere-egu22-9481, 2022.