Electron acceleration driven by the lower-hybrid-drift instability

An extended quasilinear model

¹ Laboratoire Lagrange, Observatoire de la Côte d’Azur, Université Côte d’Azur, CNRS, Nice, France
e-mail: federico.lavorenti@oca.eu
² Dipartimento di Fisica “E. Fermi”, Università di Pisa, Pisa, Italy
³ LPC2E, CNRS, Univ. d’Orléans, OSUC, CNES, Orléans, France
⁴ IRAP, CNRS-CNES-UPS, Toulouse, France

Received: 11 April 2021
Accepted: 13 May 2021

Abstract

Context. Density inhomogeneities are ubiquitous in space and astrophysical plasmas, particularly at contact boundaries between different media. They often correspond to regions that exhibit strong dynamics across a wide range of spatial and temporal scales. Indeed, density inhomogeneities are a source of free energy that can drive various instabilities such as the lower-hybrid-drift instability, which, in turn, transfers energy to the particles through wave-particle interactions and eventually heats the plasma.

Aims. Our study is aimed at quantifying the efficiency of the lower-hybrid-drift instability to accelerate or heat electrons parallel to the ambient magnetic field.

Methods. We combine two complementary methods: full-kinetic and quasilinear models.

Results. We report self-consistent evidence of electron acceleration driven by the development of the lower-hybrid-drift instability using 3D-3V full-kinetic numerical simulations. The efficiency of the observed acceleration cannot be explained by standard quasilinear theory. For this reason, we have developed an extended quasilinear model that is able to quantitatively predict the interaction between lower-hybrid fluctuations and electrons on long time scales, which is now in agreement with full-kinetic simulations results. Finally, we apply this new, extended quasilinear model to a specific inhomogeneous space plasma boundary, namely, the magnetopause of Mercury. Furthermore, we discuss our quantitative predictions of electron acceleration to support future BepiColombo observations.