Hybrid-Kinetic Approach: Inertial Electrons

TL;DR

This paper reviews hybrid-kinetic simulation models that incorporate finite electron mass, highlighting their importance in accurately modeling space plasma phenomena like magnetic reconnection and turbulence.

Contribution

It provides a comprehensive review of hybrid-kinetic models with finite electron mass and demonstrates their implementation through the CHIEF code.

Findings

Finite electron mass affects magnetic reconnection dynamics.

Inclusion of electron inertia improves simulation accuracy.

The CHIEF code effectively models electron mass effects.

Abstract

Hybrid-kinetic simulations describe ion-scale kinetic phenomena in space plasmas by considering ions kinetically, i.e. as particles, while electrons are modelled as a fluid. Most of the existing hybrid-kinetic codes neglect the electron mass (see chapter 3) for a simplified calculation of the electromagnetic fields. There are, however, situations in which delay in the electrons response due to the electron inertia matters. This chapter concentrates on hybrid-kinetic simulation models which take the finite mass of the electron fluid into account. First a review is given of the history of including the finite electron mass in hybrid-kinetic models. Then the equations are discussed which additionally have to be solved compared to the mass-less hybrid-kinetic models. For definiteness their numerical implementation without additional approximations is illustrated by describing a hybrid-kinetic code, CHIEF. The importance of the consideration of the finite electron mass are discussed for typical applications (magnetic reconnection, plasma turbulence, collisionless shocks and global magnetospheric simulations). In particular the problem of guide field magnetic reconnection is addressed in some detail. Possible next steps towards further improvements of hybrid-kinetic simulations with finite electron mass are suggested.