1,- 1Swedish Institute of Space Physics (IRF), Solar System Physics and Space Technology (SSPT), Kiruna, Sweden (thomas.maynadie@irf.se)
- 2Physical Research Laboratory, Ahmedabad, 380009, India
- 3Space Science and Planetology, Physics Institute, University of Bern, Bern, CH-3012, Switzerland
- 4Japan Aerospace Exploration Agency, Kanagawa, 252-5210, Japan
While the Moon lacks a global intrinsic magnetic field, its crust features small-scale magnetized regions known as lunar magnetic anomalies [1]. Their interaction with the solar wind causes significant proton reflection and deflection [2] and creates unique structures known as lunar mini-magnetospheres [3, 4]. Previous studies have shown that lunar magnetic anomalies induce global-scale perturbations in the near-surface lunar plasma environment on both the dayside [5] and nightside [6]. In particular, simulations suggest that the largest lunar magnetic anomaly, the South Pole-Aitken (SPA) cluster, causes large-scale solar wind compressions and interplanetary magnetic field enhancements due to the interaction between protons reflected by SPA and the solar wind that can reach south-polar regions when the SPA cluster is at local noon [7]. However, the influence of these solar wind compressions on the plasma environment at the lunar South Pole remains unknown.
In this study, we produce new composite images of backscattered energetic neutral hydrogen derived from Sub-KeV Atom Reflecting Analyzer (SARA) [8] measurements. These images show that the plasma perturbations generated by the SPA cluster can extend to lunar south-polar regions, depending on local time and upstream solar wind conditions. These perturbations affect solar wind proton precipitation patterns, either decreasing or enhancing impinging proton fluxes depending on whether the south pole lies downstream or outside of the SPA anomaly. Based on these observations, we develop an empirical model of solar wind compression by the SPA cluster to evaluate its impact on ion instrument measurements at the south pole.
Understanding the complex interactions between the plasma, dust, and electromagnetic environments is an important asset to ensure safe and sustainable human presence on the Moon. We will discuss the role of the SPA cluster in these interactions, which will establish preliminary measurement requirements for in-situ plasma instruments in polar regions.
References:
[1] Coleman et al. (1972), Physics of the Earth and Planetary Interiors, https://doi.org/10.1016/0031-9201(72)90050-7.
[2] Lue et al. (2011), Geophysical Research Letters, https://doi.org/10.1029/2010GL046215.
[3] Lin et al. (1998), Science, https://doi.org/10.1126/science.281.5382.1480.
[4] Wieser et al. (2010), Geophysical Research Letters, https://doi.org/10.1029/2009GL041721.
[5] Maynadié et al. (2024), Europlanet Science Congress 2024, Berlin, https://doi.org/10.5194/epsc2024-79.
[6] Dhanya et al. (2018), Geophysical Research Letters, https://doi.org/10.1029/2018GL079330.
[7] Fatemi et al. (2014), Journal of Geophysical Research: Space Physics, https://doi.org/10.1002/2014JA019900.
[8] Barabash et al. (2009), Current Science, http://www.jstor.org/stable/24105464.
How to cite: Maynadié, T., Futaana, Y., Barabash, S., Bhardwaj, A., Wurz, P., and Asamura, K.: Effects of the South Pole-Aitken Magnetic Anomaly Cluster on the Plasma Environment at the Lunar South Pole, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–12 Sep 2025, EPSC-DPS2025-219, https://doi.org/10.5194/epsc-dps2025-219, 2025.
