We present two new methods to study the electric fields and their effect on ions and electrons in a cometary environment. One method is to look at the energy spectra of cometary ions, ions that are produced by ionisation of the gas emanating from the comet nucleus. The new production of such ions falls off with distance r to the nucleus proportionally to the fall-off of the parent neutral gas, as 1/r². For ions having been significantly accelerated, the energy of observed ions shows the electric potential difference between the point of ionisation and the observation point. When such ionisation occurs in a homogeneous electric field, the ion flux as function of energy is predicted to show a simple power law relation, the flux falling off as 1/E². This is indeed sometimes seen. We also discuss the possibility to interpret ion energy spectra in terms of somewhat inhomogeneous electric fields.

To this we can now add a new method where by comparing the speed of solar wind H⁺ and He²⁺ after interaction with the comet environment we can estimate the electric potential of the observation point relative to the upstream solar wind. Combining these methods opens up a whole new possibility to study in detail the electric fields acting on small scales when two plasma populations interact. Our study is specific to the cometary environment we are looking at, but the physical interactions we study are universal.

How to cite: Nilsson, H.: Electric fields in a small scale comet magnetosphere, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2582, https://doi.org/10.5194/egusphere-egu23-2582, 2023.

We present a numerical work in which the interaction between a comet and the solar wind is studied in 2D in the plane perpendicular to the solar wind mean field direction. Our simulations are conducted with the hybrid Particle-in-Cell (PIC) code Menura that allows for the injection of a turbulent solar wind [1].

First, we consider the case of laminar solar wind and we present a study on the equivalent Mach number of the two-ion-species (cometary and solar wind) plasma surrounding the comet. We develop an expression for the Mach number having suitable limits in the two asymptotic cases of infinite cometary and solar wind ion density; our expression is derived by extending previous studies on bi-ion plasma models [2]. Through numerical simulations in which the cometary activity is varied, we show how our Mach number is able to unambiguously describe  the existence and location of the cometary shock.

Second, we compare two runs, one with a laminar and one with a turbulent solar wind in the case of moderate cometary activity. We divide the simulation domain into the regions upstream and downstream the cometary shock. We analyze how plasma turbulence properties are affected by the passage through the shock in the case of a turbulent solar wind. Then, we divide the downstream region into three different regions identified by different solar wind-to-cometary ion density ratios. We study the downstream turbulence properties in the case of laminar and turbulent impinging solar wind and how they vary in those regions.

[1] Behar, E., Fatemi, S., Henri, P., & Holmström, M. (2022, May). Menura: a code for simulating the interaction between a turbulent solar wind and solar system bodies. In Annales Geophysicae (Vol. 40, No. 3, pp. 281-297). Copernicus GmbH.

[2] Dubinin, E. M., Sauer, K., McKenzie, J. F., & Chanteur, G. (2002). Nonlinear waves and solitons propagating perpendicular to the magnetic field in bi-ion plasma with finite plasma pressure. Nonlinear Processes in Geophysics, 9(2), 87-99.

How to cite: Pucci, F., Behar, E., Henri, P., Simon Wedlund, C., and Ballerini, G.: Plasma turbulence within cometary plasma environments, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9003, https://doi.org/10.5194/egusphere-egu23-9003, 2023.

Around 17 December 2021, the Solar Orbiter spacecraft was predicted to have had its closest approach to comet C/2021 A1 (Leonard) with a minimum streamline distance < 0.01 AU. This encounter provided an unprecedented opportunity to investigate in situ comet Leonard's interaction with the solar wind and the composition of pick-up ions produced by ionization and dissociation of outgassed neutrals from its coma. It was a long-period comet originating from the Oort Cloud with a nucleus about 1 km in diameter, with ground-based telescope observations after its perihelion pass (at ~0.62 AU on 3 January 2022) indicating that it had subsequently disintegrated. Prior to perihelion, outbursts had been reported as well as variations in brightness, which had resulted in speculation about an impending disintegration. However, the dimming in November 2021, before the Solar Orbiter encounter, was argued to be due to a transition from outgassing dominated by carbon dioxide to water. Comet Leonard was the brightest comet of the year and noted for its spectacular ion tail with complex structures, including knots and streamers. Preliminary analysis of in situ Solar Orbiter observations have revealed tell-tale signatures of a cometary encounter around the time of predicted closest approach, such as evidence for magnetic field line draping. However, the clearest evidence has come from Solar Wind Analyzer-Heavy Ion Sensor (SWA-HIS) observations of singly-charged oxygen ions, which are typically not of solar origin and are usually produced when the solar wind interacts with a comet or other Solar System body. In this presentation we use SWA-HIS and EDP-STEP data to investigate aspects of the solar wind interaction and composition of cometary pick-up ions from this active, long-period comet shortly before its disintegration.

How to cite: Stubbs, T., Galvin, A., Livi, S., Delano, K., Ellis, L., Kistler, L., Dewey, R., Raines, J., Lepri, S., Lario, D., Jones, G., Grant, S., Wurz, P., Kucharek, H., Owen, C., Fedorov, A., Louarn, P., Matteini, L., Berger, L., and Wimmer-Schweingruber, R. and the The Heavy Ion Sensor (HIS) Science Team: Solar Orbiter Observations of Ion Species during the Encounter with the Tail of Comet Leonard, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9550, https://doi.org/10.5194/egusphere-egu23-9550, 2023.

Using magnetic field data collected by Mars Atmosphere and Volatile EvolutioN (MAVEN), we investigated the external magnetic field distribution over low crustal field regions in the Martian ionosphere. Both draping and looping magnetic field are observed in the Martian dayside and nightside ionosphere at attitude range 150-600 altitude. Draping magnetic field is formed by the draped interplanetary magnetic field around the ionosphere obstacle, which is formed by the well-known induced magnetosphere current system. Looping magnetic field, observed in both ionosphere and magnetosphere, indicates a new current system coupling the ionosphere and magnetosphere. This new current system, different with the induced magnetosphere current system, has sunward component in the magnetosphere, and tailward component in the low altitude ionosphere. This current system is validated by both MAVEN observation and a global multi-fluid magnetohydrodynamic (MHD) simulation, which is most likely a universal phenomenon for a non-magnetized planetary with ionospheres interacted with high-speed solar wind.

How to cite: Gao, J., Rong, Z., Wei, Y., and Lu, H.: A new magnetosphere-ionosphere current system on Mars, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9, https://doi.org/10.5194/egusphere-egu23-9, 2023.

We apply a recently presented method to estimate ion escape to Mars. The method combines in-situ observations and a hybrid plasma model (ions as particles, electrons as a fluid). Observed upstream solar wind conditions from the Mars Atmosphere and Volatile Evolution (MAVEN)  are used as input to the model.  We then vary ionospheric ion production until the solution fits the observed bow shock location.  With this method, we investigate how upstream conditions, including solar EUV, solar wind dynamic pressure, Interplanetary Magnetic Field (IMF) strength and cone angle, affect the heavy ions loss. The results indicate that the heavy ions escape rate is higher in high EUV and the tail flux is sensitive to EUV variety while the plume is not. The ion escape rate increases as solar wind dynamic pressure increases. 

How to cite: Zhang, Q., Holmström, M., Wang, X., and Nilsson, H.: The influence of upstream conditions on heavy ion escape at Mars, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-490, https://doi.org/10.5194/egusphere-egu23-490, 2023.

Since September 2014, NASA's Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft has been measuring the in-situ ionospheric constituents of Mars. Recently, MAVEN detected the presence of large-scale plasma depletions (at least ten-fold) within the Martian ionosphere, also known as Plasma Depletion Events (PDEs). Geometrically, the Martian PDEs appear to be bubble-like plasma structures. Although the origin and formation of PDEs are not entirely understood, they are known to occur primarily on the nightside and in regions with stronger crustal magnetic fields.

In this study, we analyze the variation of magnetic field magnitude and direction and electric field power (2–100 Hz) associated with PDEs. We show that, in most cases, the magnetic fields do not considerably change within the plasma-depleted region. Conversely, the low-frequency electric field wave power is enhanced by up to two orders of magnitude at the peak depletion. Both ions and electrons within PDEs are highly magnetized. We present possible formation mechanisms of PDEs supported by recent findings.

How to cite: Basuvaraj, P., Němec, F., Regoli, L., Fowler, C., Němeček, Z., and Šafránková, J.: Ionospheric Plasma Depletions at Mars: MAVEN Observations of In-situ Plasma and Wave properties, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3122, https://doi.org/10.5194/egusphere-egu23-3122, 2023.

The Mars Ion and Neutral Particle Analyzer (MINPA), one of the three scientific payloads onboard the Tianwen-1 orbiter, was designed to measure ions and energetic neutral atoms (ENAs) at Mars. From November 2021, MINPA started to collect scientific data around Mars. Here, we present MINPA's first results of the solar-wind ENAs, which are produced through the charge exchange process between the solar wind hydrogen ions and the Martian neutral exosphere. We perform a comprehensive comparison between the inflight ENA data and ground calibration results to understand the energy and angular distributions of the solar-wind ENA signals. The possible contamination of these observations by ions and solar extreme ultraviolet (EUV) is evaluated by comparing the ENA measurements with the ion data. We will present several cases of the solar wind ENA observations, and their intensities are estimated to be 10^5~10^6 cm^-2 sr^-1 s^-1, which is in good agreement with previous in situ measurements and predictions using models.

How to cite: Ma, J., Li, W., Kong, L., Zhang, Y., Wurz, P., Galli, A., Tang, B., Xie, L., Wang, L., Qiao, F., Li, L., and Wang, C.: Solar Wind Energetic Neutral Atom Observation at Mars by MINPA Onboard the Tianwen-1 Orbiter, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5058, https://doi.org/10.5194/egusphere-egu23-5058, 2023.

Accelerated electron populations observed in the nightside ionosphere of Mars are investigated using measurements obtained by MAVEN’s Solar Wind Electron Analyzer. The measurements are of particular interest as they extend to altitudes as low as 130 km and to regions characterized by strong crustal magnetic fields, allowing us to investigate the evolution of the electron distributions in the complex crustal fields and determine the rate by which the accelerated populations precipitate into the Martian upper atmosphere.

The majority of the observed accelerated electrons are trapped in the crustal fields, bouncing between mirror points, presumably drifting across magnetic field lines, but without instantaneous access to the collisional atmosphere. The average energy flux of these electrons is significant when compared to that of the much more common ‘unaccelerated’ sheath electrons. Considering that the Martian crustal magnetic fields do not provide a closed path for drifting particles, the trapped electrons are bound to exit the crustal fields and either precipitate into the atmosphere or escape. Currently, we estimate that, despite their low detection rate (< 1%), the accelerated electrons account for about 10% of the total energy that is deposited into the nightside ionosphere by electron precipitation. Further, the peak energy of the accelerated electrons is generally found in the range of tens to hundreds of eV, consistent with the energy range previously suggested for the generation of discrete aurora emissions observed on Mars.

How to cite: Akbari, H., Fowler, C., and Andersson, L.: Precipitation of accelerated electrons at Mars, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9425, https://doi.org/10.5194/egusphere-egu23-9425, 2023.

Venus lacks a significant intrinsic magnetic field, and thus, its atmosphere and ionosphere interact directly with the solar wind flow and magnetic field from the Sun. Interplanetary magnetic fields (IMF) can penetrate into the ionosphere when the upstream solar wind dynamic pressure is stronger than the ionospheric plasma pressure. Magnetic topology can be inferred at Venus if it is defined as the magnetic connectivity to the collisional atmosphere/ionosphere, rather than connectivity to the planet’s surface. Magnetic topology can be inferred from the pitch angle and energy distribution of superthermal (> ~1 eV) electrons. More specifically, the presence of loss cones in electron pitch angle distributions infers connectivity to the nightside collisional atmosphere and the presence of ionospheric photoelectrons (identified from electron energy distributions) indicates connectivity to the dayside collisional ionosphere. We design automated procedures to determine magnetic topology with electron and magnetic field measurements by the Venus Express spacecraft over its entire mission (2006-2014). This allows us to provide the first statistical mapping of magnetic topology at Venus. We also examine how the upstream drivers affect the low-altitude magnetic topology, revealing different magnetized states of the Venus ionosphere. We find that open and closed (a surprising topology not expected at Venus) fields cluster around the terminator and draped fields dominate other regions. Our results also reveal that there is more dayside magnetic connectivity in the -E (solar wind motional electric field) hemisphere than the +E hemisphere, and during solar maximum. During solar minimum, however, there is more nightside magnetic connectivity. Last but not the least, to understand the true nature of these magnetic topologies and broadly speaking the planet-solar wind interaction, we need to think about possible ways to measure the deeply penetrated magnetic fields at Venus and Mars.

How to cite: Xu, S., Frahm, R., Ma, Y., Mitchell, D., Luhmann, J., and Persson, M.: Statistical Mapping of Magnetic Topology at Venus, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2958, https://doi.org/10.5194/egusphere-egu23-2958, 2023.

Understanding the plasma interactions between induced Venus magnetosphere and solar wind is crucial, especially at the kinetic scale (below the proton Larmor radius). This is because different kinetic-scale electric field structures that are associated with plasma instabilities such as double layers are good indicator of wave-particle energy transfer (Malaspina et al., Geophysical Research Letters, 47, 2020). Structures such as double layers, phase-space holes can emit radio waves (Goodrich and Ergun, The Astrophysical Journal, 809, 2015) or scatter electrons with energy of the order of keV (Vasko et al., Journal of Geophysical Research: Space Physics, 122, 2017). Double layers can create plasma instabilities (Newman et al., Physical Review Letters, 87, 2001), provide heating and acceleration to different particles (Ergun et al., Journal of Geophysical Research: Space Physics, 109, 2004). These structures have already been found in several parts of the earth’s magnetosphere. But due to a lack of high resolution data, observations of these processes are sparse in the magnetospheres of the other planets. The seven encounters that the Parker Solar Probe (PSP) spacecraft will make with Venus’s induced magnetosphere will provide excellent opportunities to measure these processes in this planet. The current talk describes the presence of kinetic-scale electric field structures during the 4^th encounter of PSP with Venus’s induced magnetosphere. For this purpose, high resolution electric field data from the PSP FIELDS instrument were used with alongside the FIELDS magnetometer data and data from the Solar Wind Electrons Alphas and Protons (SWEAP) instrument. From these observations, it is found that the PSP passed through Venus’s magnetosheath and tail region during this encounter.  This talk describes the possible presence of plasma double layers when PSP was at the boundary of the magnetosheath region. Phase-space holes are also identified near some of the double layers in this region.

How to cite: Sur, D. and Malaspina, D.: Observation of Possible Kinetic Structures at the Venus Magnetosphere using High Resolution Parker Solar Probe Data, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14802, https://doi.org/10.5194/egusphere-egu23-14802, 2023.

On August 10, 2021, the Mercury-bound BepiColombo spacecraft flew for the second time by Venus for a Gravity-Assist Maneuver. During this second flyby of Venus, a limited number of instruments were turned on, allowing unique observations of the planet and its environment. Among these instruments, the Mass Spectrum Analyzer (MSA) that is part of the particle analyzer consortium onboard the magnetospheric orbiter (Mio) was able to acquire its first plasma composition measurements in space. As a matter of fact, during a limited time interval upon approach of the planet, substantial ion populations were recorded by MSA, with characteristic energies ranging from about 20 eV up to a few hundreds of eVs. Comparison of the measured Time-Of-Flight spectra with calibration data reveals that these populations are of planetary origin, containing both Oxygen and Carbon ions. The Oxygen observations are to some extent consistent with previous in situ measurements from mass spectrometers onboard Venus Express and Pioneer Venus Orbiter. On the other hand, the MSA data provide the first ever in situ evidences of Carbon ions in the near-Venus environment at about 6 planetary radii. We show that the abundance of C+ amounts to about ~30% of that of O+. Furthermore, Changes in the orientation of the magnetic field suggest that these planetary ions are located in the distant magnetosheath flank in the immediate vicinity of the bow-shock region.

How to cite: Hadid, L. and the BepiColombo - MSA team (and members from MIA, MEA and MPO-MAG teams): Evidence of planetary Oxygen and Carbon ions in the outer flank of Venusmagnetosheath, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7071, https://doi.org/10.5194/egusphere-egu23-7071, 2023.

On June 23^rd 2022, BepiColombo performed its second gravity assist maneuver (MFB2) at Mercury. Just like the first encounter with Mercury that took place on October 1^st 2021, the spacecraft approached the planet from dusk-nightside to dawn-dayside down to an extremely close distance (within about 200 km altitude from the planet surface). Even though BepiColombo is in a so-called “stacked configuration” during cruise, meaning that the instruments cannot be fully operated yet, these instruments can still make interesting observations. Particularly, despite their limited field-of-view, the particle sensors allow us to get a hint on the ion composition and dynamics very close to the planet well before the forthcoming orbit insertion around Mercury in December 2025. In this study, we present observations of the Mass Spectrum Analyzer (MSA) at Mercury during MFB2. MSA is part of the low energy sensors of the Mercury Plasma Particle Experiment (MPPE) consortium (PI: Y. Saito), which is a comprehensive instrumental suite for plasma, high-energy particle and energetic neutral atom measurements (Saito et al., 2021) onboard the Mercury Magnetospheric Orbiter (Mio). MSA is a “reflectron” time-of-flight spectrometer that provides information on the plasma composition and the three-dimensional distribution functions of ions with energies up to ~ 38 keV/q and masses up to ~ 60 amu (Delcourt et al., 2016). In this study, we show that both H⁺ and He²⁺ ions in the 1-10 keV range are present throughout the innermost magnetosphere near closest approach. In addition, during this MFB2 sequence, MSA observations provide evidences of He⁺ ions with energies of several hundreds of eVs. These ions likely originate from the planet exosphere and are rapidly circulated within the magnetosphere. During the outbound sequence of MFB2, MSA measurements also reveal copious amounts of keV protons of solar wind origin that propagate upstream after being reflected from the bow shock.

How to cite: Delcourt, D., Hadid, L., Saito, Y., Fränz, M., Yokota, S., Fiethe, B., Verdeil, C., Katra, B., Leblanc, F., Fischer, H., Harada, Y., Fontaine, D., Krupp, N., Michalik, H., Illiano, J.-M., Berthelier, J.-J., Krüger, H., Murakami, G., and Matsuda, S.: BepiColombo second Mercury flyby :  Ion composition measurements from the Mass Spectrum Analyzer (MSA), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3369, https://doi.org/10.5194/egusphere-egu23-3369, 2023.

BepiColombo was launched in October 2018 and is currently en route to Mercury. Although its orbit insertion is planned for December 2025, BepiColombo will acquire new measurements during planetary flybys. During the cruise phase, the two spacecraft are docked together with Mio being protected behind the MOSIF sun shield. Thus, only partial observations of plasma distribution functions can be obtained by the Mercury Plasma Particle Experiment (MPPE) onboard Mio. However, since electrons have small Larmor radii and more isotropic distributions even in the solar wind, the two Mercury Electron Analyzer (MEA) of MPPE will provide us with new and unique measurements in the range of 5 eV to 3 keV when in solar wind mode and 3 eV to ~ 26 keV when in magnetospheric mode. We will present the interesting observations obtained by MEA onboard Mio/BepiColombo during its second Mercury flyby that happened on the 23^rd of June, 2022. In particular we will focus on the properties of the low- and high-energy electron populations observed during its crossing of Mercury’s magnetosphere.

How to cite: Aizawa, S., Andre, N., Saito, Y., Persson, M., Sauvaud, J.-A., Fedorov, A., Yokota, S., Barthe, A., Penou, E., Rojo, M., and Murakami, G.: Electron populations observed by Mercury Electron Analyzer onboard Mio/BepiColombo during its second Mercury flyby, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13257, https://doi.org/10.5194/egusphere-egu23-13257, 2023.

BepiColombo MPO and Mio spacecraft encounter the Mercury magnetosphere six times from 2021 to 2025 during the flyby maneuvers. Each flyby trajectory is unique and includes the magnetospheric regions that were not covered by MESSENGER. Mio/MGF magnetic field data were successfully retrieved during the Mercury flyby-2 in June 2022 and the data were calibrated for the scientific use. The MGF measurements show a short-time intense magnetic field depression in close proximity to the planet at local midnight, which is neither expected from the earlier observations (Mariner-10, MESSENGER) nor from the hybrid plasma simulations of the Mercury magnetosphere. Both time-dependent and time-independent scenarios are possible, including the occurrence of a transient event driven by sudden changes in the solar wind (e.g., pressure puls) or in the magnetosphere (e.g., magnetic reconnection) and the crossing of a localized current layer separating the dipolar field region from the stretched tail-like magnetic field region. While more dedicated analyses (wave analysis, variation analysis), combination with the other data (plasmas and imaging), and numerical simulations for different scenarios would improve the quality of scientific interpretation of the depression event, our study demonstrates the scientific potential of BepiColombo that it will detect various kinds of transient events and localized structures in Mercury’s magnetosphere already during the flyby maneuvers.

How to cite: Schmid, D., Fischer, D., Magnes, W., Narita, Y., Volwerk, M., Baumjohann, W., Matsuoka, A., Auster, H.-U., Richter, I., Heyner, D., Plaschke, F., and Nakamura, R.: Unexpected local magnetic depression around Mercury: BepiColombo flyby-2 discovery, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12906, https://doi.org/10.5194/egusphere-egu23-12906, 2023.

Mercury possesses a miniature but dynamic magnetosphere driven primarily by the solar wind through magnetic reconnection. A prominent feature of the dayside magnetopause reconnection that has been frequently observed is flux transfer events (FTEs), which are thought to be an important player in driving the global convection at Mercury. Using the BATSRUS Hall MHD model with coupled planetary interior, we have conducted a series of high-resolution global simulations to investigate the generation and characteristics of FTEs under different solar wind Alfvénic Mach numbers (M_A) and IMF orientations. In all simulations driven by steady upstream conditions, FTEs are formed quasi-periodically with recurrence time ranging from 2 to 9 seconds, and their characteristics vary in time as they evolve and interact with the surrounding plasma and magnetic field. Our statistical analysis of the simulated FTEs reveals that the key properties of FTEs, including spatial size, traveling speed and core field strength, all exhibit notable dependence on the solar wind M_A and IMF orientation, and the trends identified from the simulations are generally consistent with previous MESSENGER observations. It is also found that FTEs formed in the simulations contribute a significant portion of the total open flux created at the dayside magnetopause that participates in the global circulation, suggesting that FTEs indeed play an important role in driving the Dungey cycle at Mercury.

How to cite: Jia, X. and Li, C.: Global Hall MHD simulations of Mercury's magnetosphere: Formation and properties of flux transfer events (FTEs) under different solar wind conditions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10183, https://doi.org/10.5194/egusphere-egu23-10183, 2023.

Mercury possesses a weak planetary dipole moment and is subject to a strong solar wind inflow. Thus, a small magnetosphere is formed. On the nightside, a neutral current sheet elongates the magnetic field lines to form a magnetotail. From hybrid simulations it is known that this current sheet reacts to changes in the interplanetary magnetic field (IMF). In order to understand the magnetospheric reaction to changes in the solar wind, it is essential to further assess the neutral current sheet movements. The strongly radial IMF at Mercury facilitates magnetopause reconnection in high latitudes which decreases the magnetic pressure in one of the magnetospheric lobes depending on the radial IMF polarity. This produces a northward (or southward) shift of the neutral sheet. Here, we present statistical results from in-situ MESSENGER magnetic field data analysis on the IMF direction as well as the neutral sheet displacement. MESSENGER was a single probe in orbit around Mercury and, as such, it was blind to the solar wind state after having entered the bow shock. Thus, we need to estimate the current IMF radial polarity for the time frame with the probe located inside the magnetosphere. For this, we evaluate different interpolation methods with an adapted bootstrap analysis method on data taken within the upstream solar wind at Mercury. Eventually, the outcome of the statistical analysis on the neutral sheet displacement is compared to the results from hybrid simulations done in the past.

How to cite: Heyner, D., Pump, K., Hercik, D., Exner, W., Narita, Y., Plaschke, F., Schmid, D., Slavin, J., and Volwerk, M.: Neutral Current Sheet Displacement in Reaction to the Radial Interplanetary Magnetic Field at Mercury: Statistical Results from MESSENGER Data., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11546, https://doi.org/10.5194/egusphere-egu23-11546, 2023.