# Turbulence in Three-Dimensional Simulations of Magnetopause Reconnection

## TL;DR

This paper analyzes turbulence in 3D particle-in-cell simulations of magnetopause reconnection, revealing electromagnetic turbulence driven by ion pressure gradients that influences reconnection dynamics and electric fields.

## Contribution

It identifies the turbulence as a variant of the lower hybrid drift instability and links simulation results to MMS observations, highlighting its impact on reconnection scales.

## Key findings

- Turbulence develops around the X line and separatrices.
- Electric field fluctuations reach ±10 mV/m, exceeding the reconnection electric field.
- Turbulence alters scale lengths and enhances anomalous resistivity.

## Abstract

We present detailed analysis of the turbulence observed in three-dimensional particle-in-cell simulations of magnetic reconnection at the magnetopause. The parameters are representative of an electron diffusion region encounter of the Magnetospheric Multiscale (MMS) mission. The turbulence is found to develop around both the magnetic X line and separatrices, is electromagnetic in nature, is characterized by a wave vector $k$ given by $k\rho_e\sim(m_eT_e/m_iT_i)^{0.25}$ with $\rho_e$ the electron Larmor radius, and appears to have the ion pressure gradient as its source of free energy. Taken together, these results suggest the instability is a variant of the lower hybrid drift instability. The turbulence produces electric field fluctuations in the out-of-plane direction (the direction of the reconnection electric field) with an amplitude of around $\pm 10$~mV/m, which is much greater than the reconnection electric field of around $0.1$~mV/m. Such large values of the out-of-plane electric field have been identified in the MMS data. The turbulence in the simulations controls the scale lengths of the density profile and current layers in asymmetric reconnection, driving them closer to $\sqrt{\rho_e\rho_i}$ than the $\rho_e$ or $d_e$ scalings seen in 2-D reconnection simulations, and produces significant anomalous resistivity and viscosity in the electron diffusion region.