Stability analysis of electron core-strahl solar wind distributions

Abstract:

In this work, we perform kinetic stability analysis of a solar wind electron distribution made up of core and strahl subpopulations. Following up from a stability analysis in (Horaites et. al. 2018), the core population is modeled using a drifting Maxwellian and the strahl population by an analytic expression derived in (Horaites & Boldyrev 2019) from a drift kinetic equation. The updated expression for the strahl distribution used in this work differs from the previous work as the derivation is general to electrons at all energies rather than the limiting case of suprathermal particles. Linear stability analysis is performed with the LEOPARD solver (Astfalk & Jenko 2017), a dispersion solver that can input arbitrary gyrotropic distribution functions for a magnetized plasma. Stability of kinetic Alfven, magnetosonic, and whistler modes is accessed at oblique angles of propagation at a range of spacial scales. Whistler turbulence has been invoked as a source of anomalous scattering of strahl electrons, so particular interest is taken in stability of these modes.

Astfalk P., Jenko F., 2017, J. of Geophys. Research (Space Physics), 122, 89

Horaites K., Astfalk P., Boldyrev S., Jenko F., 2018, MNRAS 480, 1499-1506

Horaites K., Boldyrev S., 2019, MNRAS 489, 3412–3419