Effect of the electronic pressure on the energy and magnetic moment of charged test particles in turbulent electromagnetic fields

TL;DR

This study uses numerical simulations to investigate how the electronic pressure term in electromagnetic fields influences the acceleration and magnetic moments of charged particles in turbulent plasma, revealing new parallel energization mechanisms.

Contribution

It highlights the significance of the electronic pressure term in particle acceleration, a previously overlooked aspect in turbulent electromagnetic environments.

Findings

Electronic pressure causes parallel acceleration of protons.

EP structures are thin, elongated, and located on a near-zero background.

EP term significantly affects particle energization dynamics.

Abstract

In this work we perform direct numerical simulations of three-dimensional magnetohydrodynamics with a background magnetic field, representing solar wind plasma, and introduce test particles to explore how a turbulent electromagnetic environment affects them. Our focus is on the terms of the electric field present in the generalized Omh's Law that are usually dismissed as unimportant. These are the Hall and the electronic pressure (EP) terms, but we concentrate primarily on the latter. We discover that the EP term generates an acceleration of the particles, which represent protons, in the direction parallel to the background magnetic field, in contrast to the known preferential perpendicular energization. By studying the electric field itself, we are able to detect the type of structures of the EP field that produce such parallel acceleration. These are thin and elongated structures placed on top of a monotonic and near-zero background. A statistical study to understand the real significance of the electronic pressure term is also performed.