Three-dimensional magnetic reconnection in particle-in-cell simulations of anisotropic plasma turbulence

TL;DR

This study uses 3D particle-in-cell simulations to investigate magnetic reconnection within anisotropic plasma turbulence, revealing small-scale reconnection events that heat and accelerate particles in the solar wind.

Contribution

It introduces new indicators for identifying 3D reconnection events in kinetic simulations of turbulence, linking small-scale reconnection to particle energization.

Findings

Reconnection occurs within flux ropes formed by turbulence.

Small-scale reconnection events heat and accelerate particles.

Reconnection structures are of the order of a few ion inertial lengths.

Abstract

We use 3D fully kinetic particle-in-cell simulations to study the occurrence of magnetic reconnection in a simulation of decaying turbulence created by anisotropic counter-propagating low-frequency Alfv\'en waves consistent with critical-balance theory. We observe the formation of small-scale current-density structures such as current filaments and current sheets as well as the formation of magnetic flux ropes as part of the turbulent cascade. The large magnetic structures present in the simulation domain retain the initial anisotropy while the small-scale structures produced by the turbulent cascade are less anisotropic. To quantify the occurrence of reconnection in our simulation domain, we develop a new set of indicators based on intensity thresholds to identify reconnection events in which both ions and electrons are heated and accelerated in 3D particle-in-cell simulations. According to the application of these indicators, we identify the occurrence of reconnection events in the simulation domain and analyse one of these events in detail. The event is related to the reconnection of two flux ropes, and the associated ion and electron exhausts exhibit a complex three-dimensional structure. We study the profiles of plasma and magnetic-field fluctuations recorded along artificial-spacecraft trajectories passing near and through the reconnection region. Our results suggest the presence of particle heating and acceleration related to small-scale reconnection events within magnetic flux ropes produced by the anisotropic Alfv\'enic turbulent cascade in the solar wind. These events are related to current structures of order a few ion inertial lengths in size.