1,2,3,2,1- 1Ruhr-Universität Bochum, Institut für Theoretische Physik, Computational Plasma Physics, Bochum, Germany (mahmoud.ibrahim@ruhr-uni-bochum.de)
- 2Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA
- 3Department of Physics, Faculty of Science, Benha University, Benha 13518, Egypt
Observations from the Parker Solar Probe (PSP) reveal that electrons play a crucial role in shaping coronal and solar wind dynamics (Halekas et al. 2021, 2022, 2025). We investigate how nonthermal ( κ ) and core/strahl electron distributions modify the onset threshold of the ion-ion acoustic instability (IIAI) observed by PSP between 15-25 solar radii (Mozer et al. 2021, 2023; Kellogg et al. 2024) and modeled by Afify et al. (2024). We find that (Afify et al. 2025):
- lower κ values tend to stabilize IIAI due to higher electron phase space density at the resonance velocity, which leads to enhanced Landau damping in the electrons;
- the presence of a strahl population shifts the resonance velocity with respect to that obtained with the core distribution alone, thus modifying the IIAI threshold. An effective temperature can be calculated from core and strahl parameters (Jones et al. 1975), which allows to map the core-strahl system to one with a single electron population and simplify threshold and growth rate calculations;
- Applying the field-particle correlation technique (Klein & Howes 2016) to fully kinetic Vlasov simulations reveals detailed velocity-space energy transfer in the presence of the different electron distributions (Afify et al. 2026) and indicates that Landau damping plays a significant role in reducing free energy and contributing to heating.
Future work will address the interplay between electron and ion anisotropies in low-β regimes.
References
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How to cite: Ibrahim, M. S. A. A., Dreher, J., Klein, K. G., O'Neill, S., Martinović, M. M., and Innocenti, M. E.: How do electrons shape the proton distribution functions near the Sun?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14170, https://doi.org/10.5194/egusphere-egu26-14170, 2026.
