Drift Turbulence, Particle Transport, and Anomalous Dissipation at the Reconnecting Magnetopause

TL;DR

This study uses 3D kinetic simulations to analyze drift turbulence and particle transport at the Earth's magnetopause, revealing weak anomalous dissipation and features consistent with MMS observations, enhancing understanding of magnetic reconnection.

Contribution

It provides the first detailed 3D simulation analysis of drift turbulence effects on reconnection at the magnetopause, including new insights into dissipation and particle transport mechanisms.

Findings

Weak anomalous dissipation from drift fluctuations.

Reconnection rates similar in 2D and 3D models.

Observation of magnetosheath electron beams penetrating magnetosphere.

Abstract

Using fully kinetic 3D simulations, the reconnection dynamics of asymmetric current sheets are examined at the Earth's magnetopause. The plasma parameters are selected to model MMS magnetopause diffusion region crossings with guide fields of 0.1, 0.4, and 1 of the reconnecting magnetosheath field. In each case, strong drift-wave fluctuations are observed in the lower-hybrid frequency range at the steep density gradient across the magnetospheric separatrix. These fluctuations give rise to cross-field electron particle transport. In addition, this turbulent mixing leads to significantly enhanced electron parallel heating in comparison to 2D simulations. We study three different methods of quantifying the anomalous dissipation produced by the drift fluctuations, based on spatial averaging, temporal averaging, and temporal averaging followed by integrating along magnetic field lines. Comparison of the different methods reveals complications in identifying and measuring the anomalous dissipation. Nevertheless, the anomalous dissipation from short wavelength drift fluctuations appears weak for each case, and the reconnection rates observed in 3D are nearly the same as in 2D models. The 3D simulations feature a number of interesting new features that are consistent with recent MMS observations, including cold beams of magnetosheath electrons that penetrate into the hotter magnetospheric inflow, the related observation of decreasing temperature in regions of increasing total density, and an effective turbulent diffusion coefficient that agrees with predictions from quasi-linear theory.