Observations and Models of Proton and Alpha Particle Beams at PSP Perihelia with Implications for Solar Wind Heating
Abstract
The Parker Solar Probe (PSP) Solar Wind Electrons Alphas & Protons (SWEAP)/Solar Probe Analyzers-Ions (SPAN-I) provide details of proton and alpha particle velocity distributions (VDFs), and associated kinetic wave activity detected with the FIELDS instrument. In particular the PSP observations at perihelia show that beam-core relative speed often exceeds the local Alfven speed, and that the ions temperatures are anisotropic with T _{⊥}/T_∥>1. The origin of these ion beams and the implications for solar wind plasma kinetic heating are not well known. Recent hybrid modeling results show that large amplitude Alfven waves may drive the ion beams. Motivated by PSP observations we develop 2.5D and 3D hybrid-particle-in-cell (hybrid-PIC) models of proton and alpha particle super-Alfvenic beams in the solar wind plasma. We model for the first time the combined proton and alpha ion populations with beams and drifts, for a range of parameters relevant to PSP perihelia conditions. We find that beams and drifts drive nonlinearly coupled ion kinetic instabilities with associated ion-scale wave spectra in the inner-heliospheric solar wind. The results of the hybrid models provide the nonlinear evolution of the anisotropic core-beam ion VDFs, ion relative drifts, ion temperature anisotropies, and the wave k-spectra. We model the partition of the energies of the ions (thermal and kinetic), and waves (magnetic) due to the ion-kinetic instabilities. We conclude that the unstable ion beams can provide a mechanism for dissipating kinetic and waves energy resulting solar wind plasma heating.
- Publication:
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44th COSPAR Scientific Assembly. Held 16-24 July
- Pub Date:
- July 2022
- Bibcode:
- 2022cosp...44.1087O