The induced magnetosphere in non-magnetized planets or moons, formed by the interaction between their atmosphere and stellar wind or planetary wind, is generally modulated by external magnetic field.

The magnetic field in the induced magnetosphere is believed to be dominated by the draped field. The direction of such draped field is theoretically expected to align with the y-z direction of the interplanetary magnetic field. However, observations show the opposite direction of magnetic field in the induced magnetospheres from the interplanetary magnetic field direction. Using joint observations from Tianwen-1 and MAVEN, we obtain the averaged magnetic field map of the Martian induced magnetosphere in the accurate MSE coordinate system and calculated its standard deviation. The standard deviation confirms that the averaged magnetic field distribution is consistent with the steady state assumption. The magnetic field map illustrates a clockwise rotation of the averaged magnetic field in the y-z plane, occurring in both the dayside and nightside in the Martian induced magnetosphere. According to the magnetic induction equation, this clockwise rotation of the magnetic field occurs when a difference in the speed of plasma flow exists within the magnetosphere. It should be noted that the induced magnetospheres of the other non-magnetized planets exhibit similar qualitative properties to that of Mars, suggesting that they share comparable magnetic field characteristics.

Observations of the response process of induced magnetosphere to external magnetic field are significant for understanding global dynamical processes in non-magnetized planets, and yet such observations are quite scarce. Using simultaneous observations from Tianwen-1 and Mars Atmosphere and Volatile EvolutioN (MAVEN), we report for the first time the dynamic response of the Martian induced magnetosphere to the rotation of interplanetary magnetic field from the Sun. The magnetic field in the Martian induced magnetosphere deflected as the interplanetary magnetic field rotated suddenly, and eventually stabilized (< 3.5 minutes). The convective electric field rotated in response to the interplanetary magnetic field rotation, and the pick-up oxygen ion plume emerged in minutes (< 3 minutes). These quite short recovery timescales indicate that the induced magnetosphere is a rapidly dynamic system, and is highly sensitive to external magnetic field. It cautions us that change of interplanetary magnetic field should be considered as one of the general types of space weather on Mars, and it is essential of monitoring and short-term forecasting of interplanetary magnetic field upstream of Mars.

How to cite: Lin, R., Huang, S., Yuan, Z., Wu, H., Jiang, K., Wang, Y., Zhang, T., Xu, S., Dong, Y., Xiong, Q., and Huang, H.: Steady-state of the Martian induced magnetosphere and its rapid response to interplanetary magnetic field rotation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1237, https://doi.org/10.5194/egusphere-egu24-1237, 2024.

When the solar wind encounters the ionosphere of an unmagnetized planet, it induces currents, forming an induced magnetosphere. These currents, along with their associated magnetic fields, play a crucial role in controlling the movement of charged particles, and are essential for understanding the escape of planetary ions. Unlike the well-documented magnetospheric current systems, the ionospheric current systems on unmagnetized planet remain less understood, limiting our ability to quantify electrodynamic energy transfer. Here, using 8 years of data from the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission, we provide the first global map of the Martian ionospheric currents. We identified two current systems coexist within the ionosphere: one aligning with the solar wind electric field, with asymmetries between the west-east electric hemispheres and driven by the solar wind; and one characterized by two current vortices on the dayside, powered by the atmospheric neutral winds. Our findings indicate that the Martian ionospheric dynamics are influenced by both the neutral winds from below and the solar wind from above, emphasizing the intricate nature of current systems on unmagnetized planets.

How to cite: Gao, J., Mittelholz, A., Rong, Z., persson, M., Shi, Z., Zhang, C., Wang, X., and Wei, Y.: Characterizing the current systems in the Martian ionosphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1710, https://doi.org/10.5194/egusphere-egu24-1710, 2024.

Mars is typically regarded as a non-magnetic planet. Currents in the Martian ionosphere generate a Venus-like induced magnetosphere which deflects the solar wind flows and piles up the interplanetary magnetic fields. However, crustal magnetic fields in the southern hemisphere influence local plasma properties. Using observations from the MAVEN mission, we characterize the distinguishing plasma characteristics of a mini-magnetosphere that forms on the Martian dayside. We establish three criteria to differentiate this mini-magnetosphere from the induced magnetosphere. Notably, the mini-magnetosphere exhibits higher plasma beta (values near 1), with a balance between planetary ions, crustal magnetic fields, and the solar wind at the magnetopause. Observations show that the crustal magnetosphere reaches an altitude of 1,300 km, larger than one-third of the Martian radius, indicating a dichotomy between the induced northern and the crustal southern magnetospheres. These findings offer novel insights into the distinctive properties of hybrid magnetospheres in the near-Mars space.

How to cite: Fan, K., Wei, Y., Fraenz, M., Cui, J., He, F., Yan, L., Chai, L., Zhong, J., Rong, Z., and Dubinin, E.: Observations of a Mini-Magnetosphere Above the Martian Crustal Magnetic Fields, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2228, https://doi.org/10.5194/egusphere-egu24-2228, 2024.

Based on magnetic field and plasma measurements from the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission, we present the first observation of magnetic reconnection occurring between the closed crustal magnetic field and the Ion Composition Boundry(ICB) at the dayside of Mars. Notably, distinctive typical features typical of reconnection, such as the Hall magnetic field and plasma outflow, have been unambiguously detected. Our findings robustly support the occurrence of reconnection at Mars, specifically highlighting the interaction between the interplanetary magnetic field in the induced magnetosphere and the closed crustal magnetic field. This reconnection event induces significant alterations in the magnetic field topology, exerting a profound influence on the escape dynamics of ions.

How to cite: Qiu, X. and Yu, Y.: Observations of magnetic reconnection between the crustal magnetic field and the ICB at Mars, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5676, https://doi.org/10.5194/egusphere-egu24-5676, 2024.

The absence of a global magnetic field at Mars results in a direct interaction between the solar wind and the ionosphere, leading to ion escape from its atmosphere to space. However, the existence and asymmetric distribution of crustal fields introduce significant complexity into the plasma dynamics within the Martian environment, resulting from a disordered magnetic field topology characterized by its orientation parallel, directed towards, and away from the Martian surface. Based on three-dimensional multifluid magnetohydrodynamic simulations, we investigated the impact of the magnetic inclination angle on the Martian ionospheric plasma dynamics under the typical solar wind conditions. Numerical results showed that ions can be effectively diffuse upwards along vertical magnetic fields driven by the electron pressure gradient and the motional electric force, leading to a strong outward flux escaped through plume and the magnetotail eventually. In addition, due to the Hall electric force, there is a tendency for ion flow to be deflected in the horizontal plane. These results provide valuable insights into the influence of magnetic fields on ion motion in the Martian space environment.

How to cite: Li, S., Lu, H., Cao, J., Cui, J., Chen, N., Song, Y., and Wang, J.: The Impact and Mechanism of Magnetic Fields on Plasma Dynamics in the Martian Space Environment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4227, https://doi.org/10.5194/egusphere-egu24-4227, 2024.

Extensive research efforts have revealed that the Martian dust storms can perturb the upper atmospheric condition and as a consequence, enhance plasma density and photoelectron flux in the ionosphere. However, previous observational studies of the Martian dust storm impacts have been restricted to regions below 400 km, which limits our understanding of the Martian dust storm effects in the upper ionosphere and magnetosphere. Here, based on the suprathermal electron measurements made by the Solar Wind Electron Analyzer onboard the Mars Atmosphere and Volatile Evolution, we identify with an automatic procedure the occurrences of all photoelectron boundary (PEB) crossings at solar zenith angle below 120° (with a dust-free median altitude of about 600 km). Using the dayside PEB as a proxy of the upper ionospheric and magnetospheric condition, we analyze the variations of the PEB altitude during the 2018 global dust storm (GDS) of Mars Year 34 (MY34) and compare them with the period in MY33 when there was no global dust storm. We conclude that the column dust optical depth (CDOD) emerges as one of the main driving factors for PEB altitude variations during the GDS. Our analysis implies that the GDS can affect the Martian upper atmosphere and ionosphere over considerable distances and extended time scales.

How to cite: Wang, Y., Wei, Y., and Fan, K.: The response of Martian photoelectron boundary to the 2018 global dust storm, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2891, https://doi.org/10.5194/egusphere-egu24-2891, 2024.

Mars once had a dense atmosphere enabling liquid water existing on its surface, however, much of that atmosphere has since escaped to space. We examine how incoming solar and solar wind energy fluxes drive escape of atomic and molecular oxygen ions (O⁺ and O₂⁺) at Mars. We use MAVEN data to evaluate ion escape from February 1, 2016 through May 25, 2022. We find that Martian O⁺ and O₂⁺ have increased escape flux with increased solar wind kinetic energy flux. Increased solar wind electromagnetic energy flux also corresponds to increased O⁺ and O₂⁺ escape flux. Increased solar irradiance (both total and ionizing) does not obviously increase escape of O⁺ and O₂⁺. Together, these results suggest that the solar wind electromagnetic energy flux should be considered along with the kinetic energy flux, and that other parameters should be considered when evaluating solar irradiance’s impact on O⁺ and O₂⁺ escape.

How to cite: Schnepf, N., Dong, Y., Brain, D., Hanley, G., Peterson, W., Strangeway, R., Thiemann, E., Halekas, J., Espley, J., Eparvier, F., and McFadden, J.: Solar and solar wind energy drivers for O+ and O2+ ion escape at Mars, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2924, https://doi.org/10.5194/egusphere-egu24-2924, 2024.

The ion composition of the Martian ionosphere is controlled by the ionisation of the neutral species (mainly CO₂, CO and O) in the upper atmosphere and the chemical reactions that follow. The primary ions, CO₂⁺ and O⁺, are reactive with O and CO₂, respectively, as to produce O₂⁺, which is the dominant ion species in the ionosphere. We apply a variety of simple chemical schemes to model the ion chemistry in the Martian dayside ionosphere using data from deep dip campaigns of the MAVEN mission. As model input we use concentrations of neutral species, as measured by the Neutral and Gas Ion Mass Spectrometer (NGIMS) onboard MAVEN, and solar EUV spectra measured by TIMED/SEE; extrapolated in distance and phase to Mars. We reach an adequate agreement between the calculated ion densities of the main ion species and those measured by NGIMS. However, the calculated ion composition does not fully match the measurements and deviations of up to a factor of 3-4 do prevail for some of the considered ion species. Several previous studies have solved similar issues by adjusting the input parameters to the calculations, such as increasing the neutral O density, reducing the neutral CO₂ density or decreasing the solar irradiance. We present results from a thorough exploration of the involved parameter space and discuss possible reasons for still persisting model-observation discrepancies.

How to cite: Persson, M. and Vigren, E.: Ion chemistry in the Martian dayside ionosphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7998, https://doi.org/10.5194/egusphere-egu24-7998, 2024.

Understanding the zenith angle dependence of the Martian surface radiation environment is crucial for planning future human exploration missions to Mars. In our previous research (Wimmer et al. 2015; Guo et al. 2021; Khaksarighiri et al. 2023) we extensively studied the zenith-angle dependence of the Martian surface radiation dose rate. Leveraging the same validated radiation model, calibrated with data from the Radiation Assessment Detector (RAD) on Mars, we calculated the flux of secondary downward particles reaching to the surface of Mars from various zenith angles resulting from the interaction of primary particles with the Martian atmosphere. 

These flux of secondary particles, coming from different zenith angles, can be integrated into a comprehensive topographic map of Mars, providing a detailed depiction of the global radiation landscape.
The construction of this radiation map requires careful consideration of various factors, including atmospheric column density, local and large-scale topography offering potential shielding effects, and the input spectrum is affected by heliospheric modulation. Additionally, accounting for seasonal pressure cycles and daily atmospheric surface pressure due to thermal tides is essential. Our model specifically focused on the influence of zenith angle on atmospheric column depth and simulations tailored to the Gale Crater region, a region explored by the Curiosity rover. 

Applying this methodology allows us to create lookup tables of all secondary particles reaching the Martian surface from various zenith angles and evaluate the atmospheric impact. Employing these matrices alongside the incident spectrum enables the calculation of secondary particle flux from all zenith angles on the Martian surface.

This method provides valuable insights into the fluctuations in radiation flux on Mars, facilitating thorough assessments of potential radiation hazards. Mission planners can leverage these data, obtaining vital information to identify secure landing areas and sheltered regions for astronauts on the Martian surface.

How to cite: Khaksarighiri, S., Wimmer-Schweingruber, R. F., stubbs, T. J., Phipps, P. H., Looper, M. D., Guo, J., Ehresmann, B., Hassler, D. M., Matthiä, D., Zeitlin, C., Löwe, J. L., Berger, T., Löffler, S., and Reitz, G.: The Martian Surface Radiation Environment: Zenith Angle Dependence of Fluxes of Different Secondary Particle Species Produced in the Mars Atmosphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10518, https://doi.org/10.5194/egusphere-egu24-10518, 2024.

The Radiation Assessment Detector (RAD) onboard the Mars Science Laboratory's Curiosity rover is the first-ever instrument continuously monitoring energetic particles on the surface of Mars. Since the rover's landing on August 6, 2012, RAD has accumulated valuable data, providing an unprecedented opportunity to assess the radiation environment across a solar cycle on an another planet.
Understanding the radiation environment on Mars is crucial for a more accurate assessment of the risks posed to manned future space missions. Moreover, it also serves to further investigate planetary conditions, properties of the Sun, and galactic cosmic rays (GCRs). 
 
The radiation field on the surface of Mars primarily consists of charged particles, including primary GCRs propagating to the Martian surface and secondary particles generated through the interaction of primary GCRs with the Martian atmosphere or soil. 
Furthermore, it undergoes temporal changes caused by factors such as atmospheric pressure variations due to thermal tides, seasonal changes, geographical and topographical shielding effects, heliospheric modulation of GCRs, as well as Martian soil and subsurface conditions. Considering all these factors is essential for a comprehensive description of the radiation environment.
 
 Here we utilize the extensive RAD dataset spanning the last 11 years to delve into the intricate variations in particle flux. Our analysis encompasses a diverse array of particle species, providing a comprehensive understanding of how particle flux evolves over the course of one complete solar cycle. This extended time frame allows us to capture and analyze long-term trends, offering valuable insights into the dynamic nature of particle interactions within the Martian environment. By exploring the temporal patterns of particle flux across different species, we aim to contribute to a more nuanced comprehension of the complex radiation dynamics on Mars and its implications for future space missions and potential habitation. 
 
Additionally, we endeavored to understand the impacts of subsurface composition on the Martian surface radiation field, particularly in generating additional upward particles. This investigation is significant as it contributes to the exploration of potential subsurface water content on the surface of Mars.

How to cite: Löwe, J. L., Wimmer-Schweingruber, R., Khaksarighiri, S., Hassler, D., Guo, J., Ehresmann, B., Zeitlin, C., Matthiä, D., Berger, T., Reitz, G., and Löffler, S.: 4000 Sols on Mars - A Long-term Study of Radiation Variations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10573, https://doi.org/10.5194/egusphere-egu24-10573, 2024.

The Mars Ion and Neutral Particle Analyzer (MINPA), one of the seven scientific payloads onboard the Tianwen-1 orbiter, was specifically designed to investigate the interaction between the solar wind and Mars by analyzing ions and energetic neutral atoms (ENAs). Commencing its scientific data collection in November 2021, MINPA successfully completed its first far-magnetotail survey during the summer of 2022. Our presentation will provide a comprehensive overview of MINPA's in-flight operations and its initial scientific findings. Regarding ENA observations, MINPA achieved successful data collection during solar wind, magnetosheath, and nightside observations. An algorithm has been developed to convert ENA count rates into intensity. A statistical analysis of solar wind ENAs revealed a neutralization rate of the solar wind at the flanks of the Mars magnetosphere. We also performed a collaborative analysis using MINPA data and numerical modeling to gain a deeper understanding of the ENA spectrum and its properties. In the ion component, MINPA observed hydrogen and heavy ions across various regions at Mars. With a far apoapsis, MINPA measured heavy ion escape in the far magnetotail, showcasing significant enhancements during periods of coronal mass ejection (CME) impacts. To enhance our understanding of the Martian space environment, an interdisciplinary team, comprising scientists from the Tianwen-1, Emirates Mars Mission (EMM), Mars Atmosphere and Volatile Evolution (MAVEN), and Mars Express missions, has been assembled within the ISSI framework.

How to cite: Li, W., Kong, L., and Ma, J.: Tianwen-1 MINPA in-flight operation and first science results, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4015, https://doi.org/10.5194/egusphere-egu24-4015, 2024.

The Martian magnetotail serves as an important channel for the escape of planetary ions, with abundant dynamic processes. After Tianwen-1 successfully entered the scientific orbit around Mars, the sun is becoming increasingly active. With the orbital apoapsis ~10,760 km, Tianwen-1 completed its first magnetotail phase from March to July 2022, providing a good opportunity to investigate the response of the Martian far magnetotail to interplanetary coronal mass ejections (ICMEs). We made a preliminary analysis of the dynamic tail under an ICME impact on 16 May 2022, with Tianwen-1 monitoring magnetotail and Mars Atmosphere and Volatile EvolutioN (MAVEN) providing upstream measurements. Based on MAVEN observations, the arrival of the ICME was determined to be around 05:10 UT on 16 May 2022. Subsequently, a significant increase in the energy levels of H⁺ and O⁺ ions was seen when Tianwen-1 entered the magnetotail about one and a half hours later. Tianwen-1 continuously detected a subset of O⁺ ions with energies exceeding 1 keV. Accordingly, the escape rate of O⁺ became ~6.2 times greater during this ICME, and the highest O⁺ enhancement happened between 1 keV and 3 keV. The disturbance lasted 39 hours before returning to a quiet level. Furthermore, we conducted a statistical analysis on the escape rate of O⁺ in the far magnetotail (attitude higher than 2 Mars radius) during 11 ICME events from March to July 2022. The ion loss rates substantially increased during ICME events, especially for O⁺ with energy above several keV. This observation suggests the presence of effective acceleration processes in the Martian tail under ICME conditions.

How to cite: Wang, L., Li, L., Li, W., Xie, L., Zhang, Y., Tang, B., Kong, L., Zhang, A., Qiao, F., and Ma, J.: The response of Martian magnetotail to interplanetary coronal mass ejection events: joint observations of Tianwen-1 and MAVEN, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10951, https://doi.org/10.5194/egusphere-egu24-10951, 2024.

An algorithm has been developed to invert the solar wind parameters from the hydrogen energetic neutral atom (H-ENA) measured in near-Mars space. Supposing the H-ENA is produced by change exchange collision between protons that originated in the solar wind and neutrals in the exosphere, an H-ENA model is established based on the magnetohydrodynamic (MHD) simulation of the solar wind interaction with Mars, to study the H-ENA characteristics. It is revealed that the solar wind H-ENAs are high-speed, low-temperature beams, just like the solar wind, while the magnetosheath H-ENAs are slower and hotter, with broader energy distribution. Assuming Maxwellian velocity distribution, the solar wind H-ENA flux is best fitted by a Gaussian function, from which the solar wind velocity, density, and temperature can be retrieved. Further investigation, based on the ENA flux simulated by the H-ENA model, reveals that the accuracy of inversed solar wind parameters is related to the angular and energy resolutions of the ENA detector. Finally, the algorithm is verified using the H-ENA observations from the Tianwen-1 mission. The upstream solar wind velocity when inversed is close to that of the in situ plasma measurement. Our result suggests the solar wind parameters inversed from H-ENA observation could be an important supplement to the dataset supporting studies on the Martian space environment, where long-term continuous monitoring of the upstream SW condition is lacking.

How to cite: Zhang, Y., Li, L., Xie, L., Kong, L., Li, W., Ma, J., Tang, B., Qiao, F., Wang, L., Jin, T., and Zhang, A.: Inversion of Upstream Solar Wind Parameters from Tianwen-1 H-ENA Observations at Mars, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13783, https://doi.org/10.5194/egusphere-egu24-13783, 2024.

Using global magnetohydrodynamics simulations, we investigate the effects of the solar wind magnetosonic Mach number and the interplanetary magnetic field (IMF) on the bow shock of Venus.  Our results reveal the following findings:  (1) The size of the Venusian bow shock is primarily determined by Mach number. An increase in Mach number results in the bow shock moving closer to Venus and a reduction in its flaring angle. (2) Both the subsolar standoff distance and the bow shock's flaring angle increase with the strength of the IMF components that are perpendicular to the solar wind flow direction (By and Bz in the VSO coordinate system), whereas the parallel IMF component (Bx) has a limited impact on the subsolar standoff distance but affects the flaring angle. (3) The cross-section of the bow shock is elongated in the direction perpendicular to the IMF on the Y-Z plane, and the elongation degree is enhanced with increasing intensities of By and Bz. (4) The quasi-parallel bow shock locates closer to the planet as compared to the quasi-perpendicular bow shock. These findings are in alignment with prior empirical and theoretical models. The influences of Mach number and IMF on the bow shock's position and geometry are attributed to the propagation of fast magnetosonic waves, showing the nature of the formation of a collisionless bow shock under the interaction of magnetized flow with an atmospheric object.

How to cite: Xu, Q.: The effects of Mach number and IMF on the location of Venus bow shock: an MHD study, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4901, https://doi.org/10.5194/egusphere-egu24-4901, 2024.

A three-dimensional, four-species multi-fluid magnetohydrodynamic (MHD) model was developed to simulate the global interaction between the solar wind and Venus during the solar maximum and solar minimum periods. The model was augmented to incorporate the production and loss of the significant ion species in the Venusian ionosphere, i. e. H⁺, O₂⁺, O⁺, CO₂⁺, taking into account chemical reactions among all species. Results of simulated Venusian induced magnetosphere, which were validated by comparing with the observations from Venus Express, suggest that the shock locations are closer to the planet during the solar minimum condition, because the magnitude of electromagnetic forces in the minimum increased to counterbalance the heightened solar wind dynamic pressure. The Venusian ionosphere simulation results show that the ionospheric density profile is more condensed during solar minimum which are consistent with previous observations and simulations. Moreover, by taking advantage of our model, functions of electromagnetic forces acting on various ion species were analyzed to explore potential mechanisms behind the differences between these two solar wind conditions. The estimated ions escape rate is much higher for the minimum condition due to increased J×B forces within the magnetotail which are cause by the compressed magnetic field lines under higher solar wind dynamic pressures. This multi-fluid MHD model could serve as an efficient tool for exploring the fine structures of the Venusian space environment system and could also find applications in the future study of distinguishing impacts caused by the variation of a single parameter.

How to cite: Chen, N., Lu, H., and Li, S.: Solar Wind - Venus Interaction During the Solar Maximum & Solar Minimum Periods: A Newly Developed Multi-Fluid MHD Model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4026, https://doi.org/10.5194/egusphere-egu24-4026, 2024.

Comets are small icy bodies originating from the outer solar system that produce an increasingly dense gas coma through sublimation as they approach perihelion. Photoionisation of this gas results in a cometary ionosphere, which interacts with the impinging solar wind, leading to large scale plasma structures. One such structure is the diamagnetic cavity: the magnetic field-free inner region that the solar wind cannot penetrate. This region was encountered many times by the ESA Rosetta mission, which escorted comet 67P/Churyumov-Gerasimenko for a two-year section of its orbit.

Within the diamagnetic cavity, high ion bulk velocities have been observed by the Rosetta Plasma Consortium (RPC) instruments. The fast ions are thought to have been accelerated by an ambipolar electric field, but the nature and strength of this field are difficult to determine analytically. Our study therefore aims to model the impact of various electric field profiles on the ionospheric density profile and ion composition. The 1D numerical model we have developed includes three key ion species (H2O+, H3O+, and NH4+) in order to assess the sensitivity of each to the timescale of plasma loss through transport. NH4+ is of particular interest, as it has been previously shown to be the dominant ion species at low cometocentric distances near perihelion. It is only produced through the protonation of NH3, a minor component of the neutral gas, and we show that this makes it particularly sensitive to the electric field.

We also compare the simulated electron density to RPC datasets, to find the electric field strength and profile which best recreate the plasma densities measured inside the diamagnetic cavity near perihelion. From this, we also constrain the radial bulk ion speed that is required to explain the observations with the model.

How to cite: Lewis, Z., Beth, A., Galand, M., Henri, P., Rubin, M., and Stephenson, P.: Constraining ion transport in the diamagnetic cavity of comet 67P, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5481, https://doi.org/10.5194/egusphere-egu24-5481, 2024.

Linear Magnetic Holes (LMHs) are magnetic field depressions generated in the solar wind upstream of planetary and cometary shock. Some of those structures are reminiscent of mirror modes, thus possibly linked to the mirror mode instability driven by a temperature anisotropy in a large plasma beta environment. LMHs have also been found downstream of the shock, which suggests that they can survive its crossing (Karlsson et al. 2022). Using the new GPU-intensive kinetic hybrid model Menura (Behar et al. 2022), we present two-dimensional (2D 3V) simulations of individual solar-wind LMHs impacting a shock in quasi-perpendicular conditions. First, we feed an analytical model of stable LMHs of various size and depth with magnetic field and density variations in antiphase, oriented along the solar wind magnetic field, into the simulation. The LMHs are then left to propagate with and into the plasma flow, eventually impacting the shock, where they may cross into the induced magnetosheath. We look at the global and local effects of such crossings and how the structures' characteristics and their immediate vicinity change over time. We apply this setup to (i) a local quasi-perpendicular shock structure created by one reflecting boundary and (ii) a global simulation of a cometary environment, and compare with observational findings. This work is part of preliminary modelling efforts preparing for the upcoming ESA/JAXA Comet Interceptor mission.

How to cite: Simon Wedlund, C., Pucci, F., Preisser, L., Henri, P., Behar, E., Ballerini, G., Califano, F., Passot, T., Sulem, P.-L., and Settino, A.: Interaction between non-linear plasma structures and collisionless shocks: magnetic holes vs cometary shock, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6135, https://doi.org/10.5194/egusphere-egu24-6135, 2024.