Electron Heat Flux and Whistler Instability in the Earth's Magnetosheath

TL;DR

This study uses MMS measurements to analyze electron heat flux in Earth's magnetosheath, revealing its dependence on magnetic field draping and limitation by whistler instability thresholds.

Contribution

It provides the first detailed characterization of electron heat flux properties and their regulation by instabilities in the Earth's magnetosheath.

Findings

Heat flux is shaped by magnetic field draping around the magnetosphere.

Heat flux increases with magnetic field strength but is not significantly altered by local processes.

Whistler instability thresholds limit the electron heat flux.

Abstract

Despite heat flux's role in regulating energy conversion in collisionless plasmas, its properties and evolution in the magnetosheath downstream of the Earth's bow shock are scarcely explored. We use MMS in situ measurements to quantify and characterize the electron heat flux in the magnetosheath. We find that the heat flux is shaped by the magnetosheath magnetic field as it drapes around the magnetosphere. While it is affected by solar wind upstream conditions and increases with magnetic field strength, it is not substantially changed by local magnetosheath processes. Also, the heat flux is limited by whistler instability thresholds.