The Mercury plasma environment is enriched in planetary ions from the tenuous neutral exosphere. We have developed a test-particle model which describes the full equation of motion for planetary ions produced from photo-ionization of the neutral exosphere. The new test-particle model is coupled to a Monte Carlo test-particle model of the neutral exosphere (Exospheric Global Model; EGM; Leblanc et al. 2017) and two hybrid-kinetic models: LatHyS (Modolo et al. 2016) and AIKEF (Müller et al. 2011). This coupling will allow us to consider the impact of non-adiabatic energization on the ion density distribution as well as the connection to seasonal asymmetries in the neutral exosphere.

We compare the density, energy and phase space density distribution of He+, O+ and Na+ from our model with observations from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) time-of-flight spectrometer Fast Imaging Plasma Spectrometer (FIPS; Raines et al. 2013). Our results indicate the presence of several interesting high-density structures both inside and outside FIPS observable energy range (E = 0.05 -13 keV), the properties of which are likely very sensitive to the upstream solar wind conditions. We present how these results may aid the interpretation of FIPS data and future measurements by BepiColombo.

How to cite: Werner, A. L. E., Leblanc, F., Chaufray, J.-Y., Modolo, R., Aizawa, S., Raines, J. M., Exner, W., and Motschmann, U.: Density, Energy and Phase Space Density Distribution of Planetary Ions He+, O+ and Na+ in Mercury's Magnetosphere, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1191, https://doi.org/10.5194/egusphere-egu21-1191, 2021.

How to cite: Moroni, M., Mura, A., Milillo, A., and Nicolas, A.: Mercury’s exospheric model for SPIDER, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7583, https://doi.org/10.5194/egusphere-egu21-7583, 2021.

The interaction between the interplanetary medium and planetary environments gives rise to different phenomena on several temporal and spatial scales. Here we use the Hilbert-Huang Transform (HHT) to characterize both local and global properties of Mercury's environment as seen during two MESSENGER flybys with different upstream solar wind conditions. Hence, we may infer that the near-Mercury environment presents some different local features with respect to the ambient solar wind, due to both interaction processes and intrinsic structures of the Hermean environment. Our findings support the ion kinetic nature of the Hermean plasma structures, with the magnetosheath being characterized by inhomogeneous ion-kinetic intermittent fluctuations, superimposed to both MHD fluctuations and large-scale field structure. We show that the HHT analysis allow to capture and reproduce some interesting features of the Hermean environment as flux transfer events, Kelvin-Helmholtz vortices, and ULF wave activity, thus providing a suitable method for characterizing physical processes of different nature. Our approach demonstrate to be very promising for the characterization of the structure and dynamics of planetary magnetic field at different scales, for the identification of boundaries, and for discriminating the different scale-dependent features of global and local source processes that can be used for modelling purposes.

How to cite: Milillo, A., Alberti, T., Ivanovski, S. L., Laurenza, M., Massetti, S., Mangano, V., Mura, A., Ippolito, A., Plainaki, C., De Angelis, E., Orsini, S., and Rispoli, R.: Dynamical features of the near-Hermean environment under different solar wind conditions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8215, https://doi.org/10.5194/egusphere-egu21-8215, 2021.

Mercury’s magnetosphere is considered to be a unique and dynamic system, primarily due to the proximity of the planet to the Sun. The interaction between solar wind and embedded Interplanetary Magnetic Field (IMF) and the dayside Hermean magnetosphere drive an electric current on the magnetopause boundary of the system. The influence of the time-dependent magnetic field generated by this magnetopause current on Mercury’s interior is key to understanding the subsurface structure of the planet, as electromagnetic induction is a valuable technique for delineating electrical properties of planetary interiors. Here we assess the impact a changing IMF direction has on the Hermean magnetopause currents, and the resulting inducing magnetic field. Analytical models of conditions at the magnetopause are combined with measurements made by MESSENGER’s magnetometer as the spacecraft crossed the subsolar magnetopause boundary during the first ‘hot season’.

These MESSENGER magnetopause boundary crossings show that the introduction of the external IMF changes the direction of the magnetopause current by ~50°, compared to the case where only the internal planetary field is considered. Analytical modelling suggests that for a heliospheric current sheet crossing without any change in solar wind dynamic pressure (an east-west reversal of the IMF polarity typical at Mercury), the inducing field at Mercury’s surface caused by the resulting magnetopause current sheet dynamics is of the order of 10% of the global planetary field. The results suggest that variability of the IMF alone can have an appreciable effect on Mercury’s magnetopause current direction and generate a significant inducing magnetic field around the planet. The arrival of the BepiColombo mission will allow this response to be further explored as a method of probing Mercury’s interior.

How to cite: Zomerdijk-Russell, S. and Masters, A.: Variability of the interplanetary magnetic field as a driver of electromagnetic induction in Mercury’s interior, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8339, https://doi.org/10.5194/egusphere-egu21-8339, 2021.

The surface of bodies without a thick atmosphere in outer space is exposed to the harsh space environment [1]. Space weathering alters its properties and leads to the formation of a tenuous exosphere. This elevated density of particles is coupled to the surface and therefore carries information about the latter. The BepiColombo mission aims to probe the composition of Mercury’s exosphere for the purpose of extracting this information [2]. However, this task requires precise models of exosphere formation [3]. Sputtering by solar wind ions is expected to be one of the main drivers for exosphere formation and models are therefore sensitive to sputtering inputs. So far, mainly simulation data are used, as experimental sputtering data for relevant materials are rare. Furthermore, available measurements have been typically performed with amorphous thin films due to use of the Quartz Crystal Microbalance (QCM) technique for sputtering measurements [4, 5]. Such a QCM is very sensitive to mass changes with resolutions in the sub mono-layer regime and is therefore an ideal tool for quantitative measurements of sputtering yields [6].

We introduce a new method for determining sputtering yields of more realistic samples, which allows to overcome the limitations of thin films while making use of the high sensitivity of QCMs. For this purpose, pellets pressed from minerals that are relevant for Mercury are used. The primary sample holder is placed on a xyzφ -manipulator, which enables switching between different samples and varying the irradiation angle α. A secondary quartz (C-QCM) is placed on an independently rotatable manipulator. This setup allows probing the angular distribution of sputtered particles by determining the mass change ∆m ion⁻¹ in dependence on the angle α_C between the sample and the C-QCM, which can lead to further improvement of exosphere models. Furthermore, mass changes of the irradiated sample due to ion implantation [7], can be untangled as only deposition of ejected particles contributes to the C-QCM signal. The use of pressed pellets enables a variation in sample parameters not accessible with thin films like crystal structure, surface roughness and porosity. Nonetheless, a QCM coated with the same material is installed on the primary sample holder in addition to the pellet for calibration.
First results with the Ca-pyroxenoid wollastonite (CaSiO3) and 2 keV Ar⁺ ions are very promising. They indicate no difference in sputtering of the amorphous thin film and the pressed wollastonite pellet for Ar⁺ irradiations. In a next step, solar wind ions will be used, which will improve the understanding of sputtering of realistic samples by solar wind ions. 

References

[1] Hapke B.: J. Geophys. Res. Planet., 106, 10039, 2001.
[2] Milillo A., et al.: Planet. Space Sci., 58, 40, 2010.
[3] Wurz P., et al.: Planet. Space Sci., 58, 1599, 2010.
[4] Szabo P. S., et al.: Astrophys. J., 891, 100, 2020.
[5] Hijazi H., et al.: J. Geophys. Res. Planets, 122, 1597, 2017.
[6] Hayderer G., et al.: Rev. Sci. Instrum., 70, 3696, 1999.
[7] Biber H., et al.: Nucl. Instrum. Methods Phys. Res. B, 480, 10, 2020.

How to cite: Biber, H., Szabo, P. S., Jäggi, N., Cupak, C., Brötzner, J., Gesell, D., Galli, A., Wurz, P., and Aumayr, F.: A novel setup to examine sputtering characteristics of mineral samples, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9896, https://doi.org/10.5194/egusphere-egu21-9896, 2021.

Mercury’s magnetic cusp allows solar wind plasma to precipitate into the magnetosphere, exosphere, and directly to the surface. This precipitation of solar wind leads to the production of neutrals in the exosphere and/or ions in the magnetosphere and thus it has an important role in shaping Mercury’s space environment. Characterizing the ion properties in the cusp region is important for obtaining a better understanding of the Sun-planet interactions and assessing the solar wind penetration in Mercury’s magnetosphere.

The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft has observed the northern cusp regularly during its orbital phase. We have analyzed plasma data obtained by the Fast Imaging Plasma Spectrometer (FIPS) onboard MESSENGER under extreme solar wind events and compared the resulting ion properties in the northern cusp with those under non-extreme solar wind events for the first time. We found that (1) flux enhancement is confirmed under the extreme solar wind, and (2) the ion distribution in the cusp has a smaller kappa value than in the magnetosheath, suggesting ion acceleration occurs in the magnetosphere.

How to cite: Aizawa, S., André, N., and Raines, J.: Ion properties of Mercury’s northern cusp under extreme solar wind observed by MESSENGER, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11897, https://doi.org/10.5194/egusphere-egu21-11897, 2021.

We explore the dynamic magnetosphere of Mercury by employing a three‐dimensional hybrid particle-in-cell (particle ions and massless fluid electrons) code – hybrid-VPIC. The newly developed hybrid-VPIC code (based on the high-performance fully kinetic Vector Particle-In-Cell, VPIC code) incorporates ion kinetics (beam and anisotropy driven instabilities) that are critical for foreshock and magnetosheath physics, as well as the Hall effect which is important for collisionless magnetic reconnection; therefore, it is particularly well suited for investigating the kinetic physics of Mercury's dynamic magnetosphere. The simulation results are in good agreement with MESSENGER’s magnetic field measurements during its second Mercury flyby. We will investigate collisionless magnetic reconnection (including flux transfer events or FTEs and ion velocity distribution functions) and foreshock physics (including plasma turbulence and particle acceleration) in this study.

How to cite: Dong, C., Le, A., Wang, L., Stanier, A., Wetherton, B., Daughton, W., Bhattacharjee, A., Slavin, J., and DiBraccio, G.: Global Hybrid-VPIC Simulations of the Solar Wind Interaction with Mercury's Dynamic Magnetosphere: Reconnection and Foreshock, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12954, https://doi.org/10.5194/egusphere-egu21-12954, 2021.

We inspect the evolution of stream interaction regions from Earth to Mars for the declining solar cycle 24. In particular, the opposition phases of the two planets are analyzed in more detail. So far, there is no study comparing the long-term properties of stream interaction regions and accompanying high-speed streams at both planets for the same time period. We build a catalogue covering a dataset of all measured stream interaction regions at Earth and Mars for the time period December 2014 – November 2018. The number of events (>120) allows for a strong statistical basis. To build the catalogue we use near-earth OMNI data as well as measurements from the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. For the opposition phase, we additionally use image data from the Solar Dynamics Observatory to complement the in-situ observations. Bulk speed, proton density, temperature, magnetic field magnitude and total perpendicular pressure are statistically evaluated using a superposed epoch analysis. For the opposition phase, coronal holes that are linked to individual streams are identified. The extracted coronal hole areas (using CATCH) and their longitudinal/latitudinal extension are correlated to the duration and maximum bulk speed of the high-speed stream following the passage of a stream interaction region. We find that an expansion of the stream interface from 1 to 1.5 AU is most visible in magnetic field and total perpendicular pressure. The duration of the high-speed stream does not increase significantly from Earth to Mars, however, the stream crest seems to increase. The amplitudes of the SW parameters are found to only slightly increase or stagnate from 1 – 1.5 AU. We arrive at similar correlation coefficients for both planets with the properties of the related coronal holes. There is a stronger linking of maximum bulk speed to latitudinal extent of the coronal hole than to the longitudinal. On average, the occurrence rate of fast forward shocks increases from Earth to Mars.

How to cite: Geyer, P., Temmer, M., Guo, J., and Heinemann, S.: Evolution of stream interaction regions from 1 to 1.5 AU, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12513, https://doi.org/10.5194/egusphere-egu21-12513, 2021.

We discuss the solar wind interaction with Mars in a self-consistent, 3-dimensional global hybrid simulation, where ions are treated as macroscopic particle clouds moving under the Lorentz force and electrons form a charge-neutralizing fluid. In the model, ion populations include both the solar wind and planetary ions. We concentrate on the formation of plasma waves near Mars. Especially, we analyze properties of large-scale waves in the ion foreshock and their transmission in the magnetosheath. Further, we study the coupling of the waves with ion dynamics in the Martian plasma environment. We discuss the solar wind interaction with Mars in a self-consistent, 3-dimensional global hybrid simulation, where ions are treated as macroscopic particle clouds moving under the Lorentz force and electrons form a charge-neutralizing fluid. In the model, ion populations include both the solar wind and planetary ions. We concentrate on the formation of plasma waves near Mars. Especially, we analyze properties of large-scale waves in the ion foreshock and their transmission in the magnetosheath. Further, we study the coupling of the waves with ion dynamics in the Martian plasma environment. Finally, we compare these Mars simulations to our earlier global hybrid modeling of Venus and Mercury to investigate how the waves and ion dynamics depend on the distance from the Sun and the size of a planetary plasma environment.

References:

Jarvinen R., Alho M., Kallio E., Pulkkinen T.I., 2020, Oxygen Ion Escape From Venus Is Modulated by Ultra-Low Frequency Waves, Geophys. Res. Lett., 47, 11, doi:10.1029/2020GL087462

Jarvinen R., Alho M., Kallio E., Pulkkinen T.I., 2020, Ultra-low frequency waves in the ion foreshock of Mercury: A global hybrid modeling study, Mon. Notices Royal Astron. Soc., 491, 3, 4147-4161, doi:10.1093/mnras/stz3257 

How to cite: Jarvinen, R., Kallio, E., and Pulkkinen, T.: Mars-solar wind interaction in a global hybrid model: plasma waves and ion dynamics, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2454, https://doi.org/10.5194/egusphere-egu21-2454, 2021.

The Martian interaction with the solar wind is unique due to the influence of multiple internal and external drivers, including remanent crustal magnetic fields that make the interaction unique. In this work we focus on the analysis of the dynamics of the plasma boundaries that shape the interaction of the planet with its environment, and in particular of the shock whose location varies in a complex way. We use multi spacecraft datasets from three missions (Mars Global Surveyor, Mars Express, Mars Atm-osphere and Volatile Evolution) to provide a coherent picture of the shock drivers. We show how the use of different statistical parameters or cross correlations may modify conclusions. We thus propose the use of refined methods, such as partial correlation analysis or Akaike Information Criterion approach to analyse the multiple drivers of the shock location and rank their relative importance: solar wind dynamic pressure, extreme ultraviolet fluxes, magnetosonic mach number, crustal magnetic fields, but also solar wind orientation parameters. Seasonal effects of crustal fields on the shock, through ionospheric coupling, are also investigated.

How to cite: Garnier, P., Jacquey, C., Génot, V., Sanchez-Cano, B., Gendre, X., Mazelle, C., Fang, X., Gruesbeck, J. R., Hall, B., Halekas, J. S., and Jakosky, B. M.: Dynamics of the Martian bow shock location, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9157, https://doi.org/10.5194/egusphere-egu21-9157, 2021.

Planetary foreshocks and magnetosheaths are regions which include many small-scale kinetic processes. Therefore, terrestrial planets Mercury, Venus, Earth and Mars provide interesting laboratories to investigate how the kinetic effects depend on the properties of the solar wind and on the properties of the planet.

The kinetic effects can be investigated with a 3D hybrid model where ions are modelled as particles accelerated by the Lorentz force. Recent studies based on our parallel hybrid model have shown that the simulation has an adequate spatial resolution to investigate, in detail, the ion 3D velocity distributions and the properties of the ULF waves at the foreshocks of Mercury, Venus and Mars.  

How to cite: Kallio, E., Jarvinen, R., Gupta, S., and Pulkkinen, T.: Foreshocks of the terrestrial planets: Simulations of kinetic effects, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7469, https://doi.org/10.5194/egusphere-egu21-7469, 2021.

High-Mach-number collisionless shocks are found in planetary systems and supernova remnants (SNRs). Electrons are heated at these shocks to temperatures well above the Rankine–Hugoniot prediction. However, the processes responsible for causing the electron heating are still not well understood. We use a set of large-scale particle-in-cell simulations of nonrelativistic shocks in the high-Mach-number regime to clarify the electron heating processes. The physical behavior of these shocks is defined by ion reflection at the shock ramp. Further interactions between the reflected ions and the upstream plasma excites electrostatic Buneman and two-stream ion–ion Weibel instabilities. Electrons are heated via shock surfing acceleration, the shock potential, magnetic reconnection, stochastic Fermi scattering, and shock compression. The main contributor is the shock potential. The magnetic field lines become tangled due to the Weibel instability, which allows for parallel electron heating by the shock potential. The constrained model of electron heating predicts an ion-to-electron temperature ratio within observed values at SNR shocks and in Saturn’s bow shock. We also present evidence for field amplification by the Weibel instability. The normalized magnetic field strength strongly correlates with the Alfvenic Mach number, as is in-situ observed at Saturn's bow shock.

How to cite: Bohdan, A., Pohl, M., Niemiec, J., Morris, P. J., Matsumoto, Y., Amano, T., Hoshino, M., and Sulaiman, A.: Kinetic simulations of high Mach shocks: PIC simulations vs in-situ measurements, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-556, https://doi.org/10.5194/egusphere-egu21-556, 2021.