Whistler-wave instability scattering of the electron strahl in the solar wind
Abstract
In the solar wind, the electrons consist of three different electron populations: core, halo, and strahl. Compared to the electron core, the electron strahl distribution shows a greater energy extending up to 100 eV and a highly anisotropic pitch-angle distribution. Since the relative strahl density decreases with heliocentric distance while the halo density increases, we investigate the possibility that the electron strahl is locally scattered by a resonant wave instability and coulomb collisions. We semi-analytically solve the quasilinear diffusion equation for wave-particle interactions, including a Fokker-Planck collision term, with the Crank-Nicolson method. We find that the electron strahl scatters into the halo through the action of the oblique whistler-wave instability and the subsequent enhancement of Coulomb collisions. We compare these solutions to results from numerical particle-in-cell simulations. These results have strong implications for the solar wind in the inner heliosphere, and we seek to discuss the connections of our work to data from Parker Solar Probe.
- Publication:
-
Solar Heliospheric and INterplanetary Environment (SHINE 2019)
- Pub Date:
- May 2019
- Bibcode:
- 2019shin.confE..93J