Bipolar Electric Field Signatures of Reconnection Separatrices for a Hydrogen Plasma at Realistic Guide Fields

TL;DR

This study uses large-scale simulations to analyze bipolar electric field signatures along reconnection separatrices in hydrogen plasmas with various guide fields, aiding MMS mission interpretation.

Contribution

It demonstrates that bipolar electric field signatures are common along reconnection separatrices across a range of guide fields in hydrogen plasmas.

Findings

Bipolar signatures are present at all guide fields studied.

Strong electron flows lead to streaming instabilities and bipolar signatures.

Results support using bipolar signatures as indicators of reconnection sites.

Abstract

In preparation for the MMS mission we ask the question: how common are bipolar signatures linked to the presence of electron holes along separatrices emanating from reconnection regions? To answer this question, we conduct massively parallel simulations for realistic conditions and for the hydrogen mass ratio in boxes larger than considered in similar previous studies. The magnetic field configuration includes both a field reversal and a out of plane guide field, as typical of many space situations. The guide field is varied in strength from low values (typical of the Earth magnetotail) to high values comparable to the in plane reconnecting field (as in the magnetopause). In all cases, along the separatrices a strong electron flow is observed, sufficient to lead to the onset of streaming instabilities and to form bipolar parallel electric field signatures. The presence of bipolar structures at all guide fields allows the control of the MMS mission to consider the presence of bipolar signatures as a general flag of the presence of a nearby reconnection site both in the nightside and in the dayside of the magnetosphere.