Dispersive and kinetic effects on kinked Alfv\'en wave packets: a comparative study with fluid and hybrid models

TL;DR

This study compares fluid and hybrid models to understand dispersive and kinetic effects on kinked Alfvén wave packets, revealing how Hall effects and proton kinetics influence wave evolution and energy transfer in low-beta plasmas.

Contribution

It provides a comparative analysis of MHD, Hall-MHD, and hybrid simulations to elucidate dispersive and kinetic effects on Alfvén wave packets in low-beta plasmas.

Findings

Hall term governs wave packet evolution over characteristic time.

Wave dispersion converts wave energy into internal plasma energy.

Proton internal energy increases due to compressions and phase space mixing.

Abstract

We investigate dispersive and kinetic effects on the evolution of a two-dimensional kinked Alfv\'en wave packet by comparing results from MHD, Hall-MHD and hybrid simulations of a low-$\beta$ plasma. We find that the Hall term determines the overall evolution of the wave packet over a characteristic time $\tau^*=\tau_a\ell/d_i$ in both fluid and hybrid models. Dispersion of the wave packet leads to the conversion of the wave energy into internal plasma energy. When kinetic protons are considered, the proton internal energy increase has contributions from both plasma compressions and phase space mixing. The latter occurs in the direction parallel to the guiding mean magnetic field, due to protons resonating at the Alfv\'en speed with a compressible mode forced by the wave packet. Implications of our results for switchbacks observations and solar wind energetics are discussed.