Contribution of Magnetic Reconnection Events to Energy Dissipation in Magnetosheath Turbulence

TL;DR

This study analyzes MMS magnetosheath data to assess how magnetic reconnection events contribute to energy dissipation, finding they have strong local dissipation but are not the primary energy dissipation mechanism overall.

Contribution

It provides a statistical analysis of magnetic reconnection events at electron scales and evaluates their role in energy dissipation in magnetosheath turbulence.

Findings

MR events have higher PVI values and stronger energy dissipation than other structures.

MR events contribute minimally to overall energy dissipation due to their small proportion.

Non-MR current sheets are mainly associated with kinetic Alfvén fluctuations.

Abstract

By analyzing the magnetosheath measurements from MMS, we obtain the statistical results for the contribution of magnetic reconnection (MR) events at electron scales to the energy dissipation of coherent structures. The Partial Variance of Increments (PVI) method is employed to find coherent structures in the magnetic field data. The current sheet structures with reversal of magnetic field components are further selected. We consider the following criteria to identify the MR events, such as current sheet with magnetic field reversal, significant energy dissipation, and evident electron outflow velocity. Statistically, for most MR events, their PVI values are larger than that of other types of coherent structures, and their energy dissipations are also stronger than that of others. However, due to the relatively small proportion of MR events, their contribution to coherent structures' energy dissipation is relatively trivial. If taken into account the dissipation of non-coherent structures, the MR's contribution to energy dissipation would be less. Hence, we suggest that MR events, though have strong dissipation locally, are not the major contributor to the energy dissipation in the magnetosheath. After analyzing the features of non-MR current sheets, we propose that non-MR current sheets are mainly coherent structures inherent to kinetic Alfv\'en fluctuations.