MITM6

On March 12, 2012, a Coronal Mass Ejection (CME) was released from the Sun with a speed of ~2000 km/s. The CME source region was surrounded by three different coronal holes (CHs), located to the East (negative polarity), South-West (positive polarity) and West (positive polarity). Its interplanetary counterpart (ICME) impacted Earth and was in-situ measured by the Advanced Composition Explorer (ACE) / Wind at L1 and the Solar TErrestrial RElations Observatory Ahead (STEREO)-A on March 15th. During this period, the angular separation between the two locations was greater than 100 degrees. Nevertheless, the in-situ measurements revealed almost identical profiles with clear markers of ICME signatures, which is evidence of one of the widest reported multi-spacecraft detection of an ICME, having STEREO-A crossing the west flank and Earth the east flank. Supra-thermal electrons show signatures of bidirectionality and isotropy/simple strahl as  the ICME crosses the different spacecraft, providing information about the eroded parts of the ICME. Certain parts might have been  eroded, possibly due to the interaction with the fast solar wind produced by the nearby CHs. We analysed the propagation of the ICME structure using remote-sensing observations from both STEREOs and Earth together with different in-situ instrumentation at ~1 au, and performed a comparison between the physical properties derived at multiple spacecraft. This study shows the importance of multi-spacecraft observations to understand the large-scale structures of ICMEs, their evolution and interaction, as well as their implications for the space-weather discipline.

How to cite: Carcaboso, F., Dumbović, M., Temmer, M., Gómez-Herrrero, R., Heinemann, S., Nieves-Chinchilla, T., Veronig, A., Jercic, V., Rodríguez-Pacheco, J., Dissauer, K., and Podladchikova, T.: Identical Interplanetary Coronal Mass Ejection Signatures with Wide Angular Separation, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-493, https://doi.org/10.5194/epsc2022-493, 2022.

In order to improve the predictions of the solar wind environment at planets, moons, comets and interplanetary spacecraft, we study the temporal evolution and spatial variation of solar wind structures. Special emphasis is put on the fast and slow solar wind stream interaction regions (SIRs or CIRs). Currently, a huge fleet of solar observatories is available throughout the inner heliosphere, hence a multi-spacecraft study of the propagation and evolution of these structures is possible. We improve solar wind predictions by removing ICME signatures from the input data to reduce the number of false alarms. Ballistic radial propagation models are refined by pressure correction at CIRs. Latitudinal effects are taken into account to improve the models and to extend our predictions to three dimensions.

How to cite: Timar, A., Opitz, A., Biro, N., Dalya, Z., Koban, G., Nemeth, Z., and Madar, A.: Temporal evolution and spatial variation of the solar wind structures throughout the heliosphere, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-993, https://doi.org/10.5194/epsc2022-993, 2022.

The escape and precipitation of planetary ions at Mercury under different solar wind conditions have been examined using a global hybrid simulation. The combination of Mercury’s weak intrinsic magnetic field and solar wind conditions at Mercury’s location results in the formation of a relatively small magnetosphere compared to that of Earth. Its magnetosphere is strongly compressed and may disappear when solar wind conditions are extreme. Under these circumstances, the solar wind can directly interact with its exosphere and surface and the escape of planetary ions is expected to be enhanced. By focusing on the dynamic pressure and interplanetary magnetic field dependence, three different solar wind conditions are used in this study. Under the extreme solar wind planetary protons shows the highest escape rates while planetary sodium ions show the smallest, indicating that the distribution of sodium ions around the planet is controlled by the size of the magnetosphere. As the Larmor radius of planetary sodium ions is larger than that of planetary protons, they cannot escape and instead precipitate onto surface during extreme solar wind conditions, when the dayside magnetosphere is well compressed. Precipitation maps of three components (solar wind protons, planetary protons, and planetary sodium ions) show that the flux from planetary plasmas is sometimes higher than solar wind plasmas, suggesting that the precipitation of planetary plasmas should be considered for the space weathering of Mercury’s surface.

How to cite: Aizawa, S., Andre, N., Persson, M., Modolo, R., Raines, J., Leblanc, F., Chaufray, J.-Y., and Nenon, Q.: Escape and precipitation of planetary ions at Mercury under different solar wind conditions, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-902, https://doi.org/10.5194/epsc2022-902, 2022.

JUICE is ESA’s first large class mission to the outer Solar System. The main objectives of JUICE are to study Jupiter and its space environment with a special focus on Jupiter’s moons Europa, Ganymede, and Callisto, and their potential habitability. In order to fulfil these objectives, the JUICE measurements need to be accurately corrected for any possible perturbations. Here, we present Spacecraft Plasma Interaction Software (SPIS) simulations of the surface charging of JUICE in the solar wind. The results will be used to correct the future JUICE measurements for the impact of the charging. 

We have used a solar wind environment model (i.e. a description of the environment covering typical values for parameters such as electron and ion densities, temperatures, and velocities, magnetic field strengths, and EUV flux) for the location where JUICE will perform its first measurements, between 1500 and 3000 R_E from Earth. The typical values for the solar wind parameters and the minimum and maximum values from the expected parameter ranges have been used to simulate the interaction in both average and “extreme” solar wind conditions. Here we present the main results from the SPIS simulations: the surface potential of the spacecraft; the potentials at the locations of the particle and field instrumentation such as the RPWI Langmuir probes and the PEP plasma analysers; the electron and ion density at the locations of the RPWI instruments and the PEP plasma analysers; the characteristics of perturbing particle populations such as photoelectron and secondary electron populations produced by the spacecraft itself; and the properties of the ion wake of the spacecraft. The detailed knowledge of the listed parameters will be used to provide accurate analyses of the first in-situ particle and field measurements performed by JUICE.

How to cite: Holmberg, M. K. G., Jackman, C., Taylor, M. G. G. T., Witasse, O., Wahlund, J.-E., Barabash, S., Altobelli, N., Cipriani, F., Déprez, G., and Huybrighs, H. L. F.: Surface charging of JUICE in the solar wind, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-603, https://doi.org/10.5194/epsc2022-603, 2022.

A Micro-Channel Plate (MCP) is a widely used component for counting particles in space. Using the background counts of MCPs on Mars Express and Venus Express orbiters operated over 17 years and 8 years, respectively, we investigate the galactic cosmic ray (GCR) characteristics in the inner solar system. The MCP background counts at Mars and Venus on a solar cycle time scale exhibit clear anti-correlation to the sunspot number. We conclude that the measured MCP background contain the GCR information. The GCR characteristics measured using the MCP background at Mars show features that are consistent with the ground-based measurement in solar cycle 24. The time lag between the sunspot number and the MCP background at Mars is found ~9 months. The shorter-term background data recorded along the orbits (with a time scale of several hours) also show evident depletion of the background counts due to the absorption of the GCR particles by the planets. Thanks to the visible planetary size change along an orbit, the GCR contribution to the MCP background can be separated from the internal contribution due to the β-decay. Our statistical analysis of the GCR absorption signatures at Mars implies that the effective absorption size of Mars for the GCR particles have a >100 km larger radius than the solid Martian body.

How to cite: Futaana, Y., Shimoyama, M., Wieser, M., Karlsson, S., Andersson, H., Nilsson, H., Wang, X.-D., Fedorov, A., Andre, N., Holmstrom, M., and Barabash, S.: Galactic Cosmic Rays at Mars and Venus: Temporal Variations from Hours to Decades Measured as the Background Signal of Onboard Micro-Channel Plates, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-633, https://doi.org/10.5194/epsc2022-633, 2022.

Introduction:  Surface sputtering by solar wind (SW) ion irradiation is an important process for understanding the surface and exosphere of airless celestial bodies such as the Moon, Mercury, and asteroids. In addition to SW ion induced sputtering, processes such as photon and electron stimulated desorption and impact vaporization, can also contribute to the exosphere formation around airless bodies. A better understanding of relative contributions of these processes is needed to interpret ground-based and spacecraft observations of the exosphere. Our focus here is on SW ion induced sputtering. Laboratory simulations are both complex and expensive. Hence, theoretical sputtering models are used to study the incoming ions, impacted surface, and sputtered atoms. The most common sputtering models, such as TRIM and SDTrimSP, use the binary collision approximation (BCA) and predict the yield and energy distribution of sputtered atoms, along with the depth of deposition and damage, all as a function of the incoming ion type, impact energy, and impact angle.

Within SDTrimSP there are several inputs that have been applied differently in previous SW sputtering simulations^1,2,3. These parameters can influence the simulated behavior of both the target and sputtered atoms. Laboratory data is often readily available for comparison with ion sputtering simulations from monatomic or simple oxide targets, and simulations can closely match experimental sputtering yields over a broad energy range. Comparatively, little work has been done to determine how the simulation parameters should be chosen for more complex targets relevant to planetary surface analogs. It is therefore of great interest to understand how sensitive sputtering behavior is to these inputs and what parameter choices best approximate SW sputtering. We have conducted a detailed sensitivity study into SDTrimSP parameters to produce a best-practice for simulating SW impacts onto the lunar surface. These results can be used to establish a more consistent methodology for simulations of SW induced sputtering.

Methods:  First, we consider the sensitivity of the SDTrimSP simulated SW sputtering behavior to several user input parameters. In all cases we simulated the effect of H or a combination of H and He onto an anorthite (CaAl₂Si₂O₈) surface. Within SDTrimSP we considered the role of the O surface binding energy (SBE), ISBV (the method of dealing with SBEs for compounds), static vs. dynamic simulations, impact energy approximations, incidence energy approximations, and the elemental composition of the SW.  For all parameters we quantified their effect on the overall sputtering yield, elemental composition of the sputtering yield, elemental surface concentration, damage production, and energy distribution of sputtered atoms. Based on these sensitivity results we recommend a best-practice for simulating SW sputtering using SDTrimSP.

Results: The predicted sputtering behavior was shown to be highly dependent on several of the SDTrimSP parameters considered. For example, previous SW simulation studies have used O SBEs between 1 and 6.5 eV, based on recommended values, fitting to experiment, and monomatomic sublimation energies. For all cases considered, the O SBE had a significant affect on the overall and elemental yield. Furthermore, dynamic simulations, which allow for the surface to change as a function of fluence, better represent the surface evolution during SW impacts. The effect of the O SBE can also be seen in the surface composition as a function of fluence (Fig 1). For an O SBE of 1 eV, strong preferential sputtering of O is observed, and the surface composition fraction is reduced from  0.6 to 0.3 at a fluence of 200 x 10¹⁶ atoms/cm². In contrast, there is almost no reduction in O surface composition for an SBE of 6.5 eV. This large depletion in surface O at an SBE of 1 eV has not been observed in previous irradiation experiments of silicates^4,5,6. Therefore, O SBEs of 1 eV are likely not representative of what would be seen for materials relevant to planetary science.

Varying the ion  incidence angle  also significantly affected the sputtering behavior. Impacts normal to the surface are often used to simulate a flat surface and can more easily be compared to experimental data. However, the surface of the Moon and Mercury consists largely of approximately spherical weathered grains. As a result, incoming SW ions are impacting the surface at many different relative angles. When oblique incidence angles are simulated the elemental and overall yields increase in all cases. For both cases there was also an increase in the peak of the damage distribution along with a reduction in depth at this peak.

Accounting for the He component in the SW leads to a 20% increase the elemental sputtering yields and and a 20% increase in the damage produced within the substrate (Fig 2). Therefore, while He makes up only 4% of the SW it accounts for over 20% of the sputtering behavior. When comparing the H and H + He options the proportion of O in the yield stays consistent. This suggests that a factor could be used to account for the He contributions.

In summary, while SDTrimSP represents a valuable tool to better understand the effect, the results are highly dependent on many user-specific parameters. This study directly quantifies these sensitivities on the SW-induced sputtering behavior and concludes with the following best-practice recommendation for SDTrimSP simulations of SW sputtering:

• 1 keV/amu impacts (96% H, 4% He) to approximate SW composition
• Dynamic simulations to allow for the behavior to evolve as a function of fluence
• Cosine distribution of impact angles onto the surface to approximate spherical grains
• Incorporation of mineral specific SBEs where possible

References:

1. Mutzke, A., et al. (2019) “IPP-report 2019-02”

2. Szabo, P. S., et al. (2018) doi: 10.1016/j.icarus.2018.05.028

3. Schaible, M. J., et al. (2017) doi: 10.1002/2017JE005359

4. Dukes, C.A., et al. (1999) doi: 10.1029/98JE02820

5. Dukes, C.A., et al. (2015) doi: 10.1016/j.icarus.2014.11.032

6. Laczniak, D.L., et al. (2021) doi: 10.1016/j.icarus.2021.114479

Fig 1. Surface composition as a function of fluence for and O SBE of 1 eV (A) and 6.5 eV (B)

Fig 2. Count of vacancies as a function of depth for different SW compositions using a cosine distribution of the impact flux vs impact angle

How to cite: Morrissey, L., Schaible, M., Tucker, O., Szabo, P., Bacon, G., Killen, R., and Savin, D.: Establishing a Best-Practice for SDTrimSP Simulations of Solar Wind Ion Induced Sputtering, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-723, https://doi.org/10.5194/epsc2022-723, 2022.