Stability of superthermal strahl electrons in the solar wind
| Autor: | P Astfalk, Stanislav Boldyrev, J. M. Schroeder |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2021 |
| Předmět: |
010504 meteorology & atmospheric sciences
Whistler FOS: Physical sciences Electron Kinetic energy 7. Clean energy 01 natural sciences Physics - Space Physics Physics::Plasma Physics 0103 physical sciences 010303 astronomy & astrophysics Solar and Stellar Astrophysics (astro-ph.SR) 0105 earth and related environmental sciences Physics Range (particle radiation) Astronomy and Astrophysics Space Physics (physics.space-ph) Physics - Plasma Physics Computational physics Plasma Physics (physics.plasm-ph) Solar wind Strahl Distribution function Astrophysics - Solar and Stellar Astrophysics 13. Climate action Space and Planetary Science Physics::Space Physics Electric current |
| Zdroj: | Monthly Notices of the Royal Astronomical Society |
| Popis: | We present a kinetic stability analysis of the solar wind electron distribution function consisting of the Maxwellian core and the magnetic-field aligned strahl, a superthermal electron beam propagating away from the sun. We use an electron strahl distribution function obtained as a solution of a weakly collisional drift-kinetic equation, representative of a strahl affected by Coulomb collisions but unadulterated by possible broadening from turbulence. This distribution function is essentially non-Maxwellian and varies with the heliospheric distance. The stability analysis is performed with the Vlasov-Maxwell linear solver LEOPARD. We find that depending on the heliospheric distance, the core-strahl electron distribution becomes unstable with respect to sunward-propagating kinetic-Alfv\'en, magnetosonic, and whistler modes, in a broad range of propagation angles. The wavenumbers of the unstable modes are close to the ion inertial scales, and the radial distances at which the instabilities first appear are on the order of 1 AU. However, we have not detected any instabilities driven by resonant wave interactions with the superthermal strahl electrons. Instead, the observed instabilities are triggered by a relative drift between the electron and ion cores necessary to maintain zero electric current in the solar wind frame (ion frame). Contrary to strahl distributions modeled by shifted Maxwellians, the electron strahl obtained as a solution of the kinetic equation is stable. Our results are consistent with the previous studies based on a more restricted solution for the electron strahl. Comment: 8 pages, 6 figures. Accepted by Monthly Notices of the Royal Astronomical Society. Removed references from abstract, added references in body. Other minor editorial changes |
| Databáze: | OpenAIRE |
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