Electron energization and the Kelvin-Helmholtz instability

Abstract:

Flow shears and related field-aligned currents are ubiquitous in the giant planet magnetospheres with, potentially, significant auroral signatures. Shear occurs from injection flows and/or transport-related flows within the magnetodisc, but perhaps the most familiar example is the Kelvin-Helmholtz (KH) instability at the magnetopause boundary. We have shown that KH-related turbulent ion heating arises due to the non-linear interaction of counter-propagating Alfven waves. Here we address the multiple pathways of electron energization due to the KH instability. Using three-dimensional hybrid simulations, we address, as a function of electron temperature, strong guide field reconnection and parallel electron energization using test particles. In particular, the electron pressure term will be used to compare the relative energization due to kinetic Alfven waves and magnetic reconnection. While there is inherent uncertainly in determining the parallel electric field in a particle-in-cell interpolation scheme, we found that strong guide field reconnection rates are of the order of 0.1, independent of the resistivity model [Stauffer et al., 2019]. Assuming that the KH instability is localized in the equatorial plane, the Alfvenic fluctuations from the hybrid simulations are used to initialize a Gyrofluid Kinetic Electron (GKE) model on a two-dimensional dipole grid [Damiano et al., 2019]. We will compare the GKE model results with local hybrid/test particle results. Additionally, the GKE model will be used to examine high latitude processes (i.e., inertial Alfven waves) to understand the comprehensive energization due to the KH instability. The results will be discussed in the context of auroral observations related flow shear drivers at Jupiter and Saturn [Grodent, 2015].