Utilizing the Hamiltonian dynamics to study resonant interactions of whistler-mode waves and electrons in the solar wind

TL;DR

This study uses Hamiltonian dynamics and simulations to analyze how large amplitude whistler waves interact with solar wind electrons, revealing mechanisms of electron scattering and distribution features.

Contribution

It introduces a Hamiltonian-based simulation approach to study wave-particle interactions and confirms the role of oblique whistlers in electron scattering in the solar wind.

Findings

Oblique whistlers efficiently scatter field-aligned electrons.

Electrons are scattered along constant Hamiltonian surfaces.

Waves can generate horn-like features in velocity distributions.

Abstract

The role of large amplitude whistler waves in the energization and scattering of solar wind electrons has long been an interesting problem in Space Physics. To study this wave-particle interaction, we developed a vectorized test particle simulation with a variational calculation of the Lyapunov exponents. From using secular perturbation theory on this Hamiltonian system of wave and particle, we confirmed that the pitch angle diffusion of the particle was along the constant Hamiltonian surface and that it was driven by the interaction with the resonance surfaces. We also showed that oblique whistlers could efficiently scatter field-aligned strahl electrons into the halo population in the solar wind. We demonstrated through simulation that these waves were capable of generating horn-like features in the velocity distribution function, similar to recent PIC simulation results in the literature.