Particle Acceleration and Heating by Turbulent Reconnection

TL;DR

This study investigates how particles gain energy in turbulent reconnection environments like the solar wind, revealing that particle energization is more efficient with current sheets and that their behavior deviates from classical Fokker-Planck models.

Contribution

The paper introduces a new method to estimate transport coefficients and demonstrates that particle energization in turbulent reconnection is anomalous, differing from standard Fermi processes.

Findings

Energization efficiency depends on electric field strength in current sheets.

Transport coefficients can be estimated from particle-scatterer interactions.

Particle evolution deviates from Fokker-Planck predictions, indicating anomalous transport.

Abstract

Turbulent flows in the solar wind, large scale current sheets, multiple current sheets, and shock waves lead to the formation of environments in which a dense network of current sheets is established and sustains "turbulent reconnection". We constructed a 2D grid on which a number of randomly chosen grid points are acting as scatterers (i.e. magnetic clouds or current sheets). Our goal is to examine how test particles respond inside this large scale collection of scatterers. We study the energy gain of individual particles, the evolution of their energy distribution and their escape time distribution. We have developed a new method to estimate the transport coefficients from the dynamics of the interaction of the particles with the scatterers. Replacing the "magnetic clouds" with current sheets, we have proven that the energization processes can be more efficient depending on the strength of the effective electric fields inside the current sheets and their statistical properties. Using the estimated transport coefficients and solving the Fokker-Planck (FP) equation we can recover the energy distribution of the particles only for the sstochastic Fermi process. We have shown that the evolution of the particles inside a turbulent reconnecting volume is not a solution of the FP equation, since the interaction of the particles with the current sheets is "anomalous", in contrast to the case of the second order Fermi process.