Anisotropic Electron Heating in Turbulence-driven Magnetic Reconnection in the Near-Sun Solar Wind

Abstract

We perform a high-resolution, 2D, 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 subelectron 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 owing to interacting ion-scale vortices. 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 present (“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 can efficiently transfer energy from the electromagnetic fields to particles.

Electron Heating Associated With Magnetic Reconnection in Foreshock Waves: Particle‐In‐Cell Simulation Analysis

“…The contribution by E || (Figure 6b) has a slight decreasing trend over time, where the median value is above 50% at the early time and below 50% later. The dominant role of E || energization is consistent with recent observations in magnetosheath turbulence where the pdf of the work done by E || to electrons is found (Xu et al, 2023), and kinetic simulations of turbulence where T e|| enhancements are found to be significant around the reconnection onset (Franci et al, 2022). For the decomposition of j e⊥ • E ⊥ , at the later time, the relative importance is consistent with the laminar reconnection studies (e.g., Dahlin et al, 2014Dahlin et al, , 2015Dahlin et al, , 2016Li et al, 2015Li et al, , 2017: the Fermi term (Figure 6c) dominates the positive contribution, and the Betatron term (Figure 6d) is negative.…”

Thermal Energy Budget of Electrons in the Inner Heliosphere: Parker Solar Probe Observations

“…We identify three potential mechanisms that could possibly provide external thermal energy sources or sinks to the electrons in the form of nonzero Ξ: turbulent heating, instabilities, and collisions. The turbulent cascade transfers energy from large scales to kinetic scales, where kinetic processes dissipate the energy in the form of heat (Tu & Marsch 1995;Breech et al 2009;Schekochihin et al 2009;Bruno & Carbone 2013;Goldstein et al 2015;Livadiotis 2019;Franci et al 2022). This form of turbulent dissipation leads to an irreversible deposition of thermal energy.…”

Anisotropy of plasma turbulence at ion scales: Hall and pressure–strain effects

“…It is not clear at what spatial scales the pressure-strain effect acts. Electron and ion energisations are expected to work at very different scales (Franci et al 2022), but comparable scales are observed in some full-particle simulations (Yang et al 2022). It is also unclear what the role of the turbulence anisotropy is (most of the present simulations are two-dimensional) and how it compares to other processes such as Hall coupling (Papini et al 2019(Papini et al , 2021.…”