Anisotropic electron heating in turbulence-driven magnetic reconnection in the near-Sun solar wind

TL;DR

This study uses high-resolution kinetic simulations to explore how turbulence-driven magnetic reconnection in the near-Sun solar wind leads to electron heating and anisotropy, highlighting the role of electron-scale structures.

Contribution

It demonstrates the occurrence of electron-only reconnection and the associated electron heating in turbulent plasma, emphasizing the importance of electron-scale structures in energy transfer.

Findings

Power spectra show multiple power-law intervals down to electron scales.

Magnetic reconnection occurs at electron inertial length current sheets.

Electron temperature increases and develops anisotropy during reconnection.

Abstract

We perform a high-resolution two-dimensional fully-kinetic numerical simulation of a turbulent plasma system with observation-driven conditions, in order to investigate the interplay between turbulence, magnetic reconnection, and particle heating from ion to sub-electron scales in the near-Sun solar wind. We find that the power spectra of the turbulent plasma and electromagnetic fluctuations show multiple power-law intervals down to scales smaller than the electron gyroradius. Magnetic reconnection is observed to occur in correspondence of current sheets with a thickness of the order of the electron inertial length, which form and shrink due to interacting ion-scale vortexes. In some cases, both ion and electron outflows are observed (the classic reconnection scenario), while in others -- typically for the shortest current sheets -- only electron jets are presents ("electron-only reconnection"). At the onset of reconnection, the electron temperature starts to increase and a strong parallel temperature anisotropy develops. This suggests that in strong turbulence electron-scale coherent structures may play a significant role for electron heating, as impulsive and localized phenomena such as magnetic reconnection may transfer energy from the electromagnetic fields to particles more efficiently than damping mechanisms related to interactions with wave-like fluctuations.