On the Role of Separatrix Instabilities in Heating the Reconnection Outflow Region

TL;DR

This paper investigates how microinstabilities at the reconnection separatrix generate electrostatic turbulence, significantly contributing to electron heating during the transition from inflow to outflow in magnetic reconnection.

Contribution

It demonstrates that separatrix instabilities lead to electrostatic turbulence that is a key electron heating mechanism, highlighting a new aspect of reconnection dynamics.

Findings

Electrostatic solitons form due to beam instabilities.

Strong flow shears cause counterstreaming electron distributions.

Electrostatic turbulence acts as a quasi-viscous heating process.

Abstract

A study of the role of microinstabilities at the reconnection separatrix can play in heating the electrons during the transition from inflow to outflow is being presented. We find that very strong flow shears at the separatrix layer lead to counterstreaming electron distributions in the region around the separatrix, which become unstable to a beam-type instability. Similar to what has been seen in earlier research, the ensuing instability leads to the formation of propagating electrostatic solitons. We show here that this region of strong electrostatic turbulence is the predominant electron heating site when transiting from inflow to outflow. The heating is the result of heating generated by electrostatic turbulence driven by overlapping beams, and its macroscopic effect is a quasi-viscous contribution to the overall electron energy balance. We suggest that instabilities at the separatrix can play a key role in the overall electron energy balance in magnetic reconnection.