Electron-only reconnection and inverse magnetic-energy transfer at sub-ion scales

TL;DR

This paper develops and validates an analytical model for electron-only magnetic reconnection in strongly magnetized plasmas, revealing faster reconnection rates at sub-ion scales and explaining inverse magnetic energy transfer through magnetic structure coalescence.

Contribution

It introduces a new analytical model for electron-only reconnection applicable at sub-ion scales, supported by numerical validation and scaling laws for magnetic energy decay.

Findings

Reconnection rates at sub-ion scales are significantly higher than at large scales.

Magnetic structures can grow to system-size scales via coalescence.

Derived scaling laws differ from those in MHD regimes.

Abstract

We derive, and validate numerically, an analytical model for electron-only magnetic reconnection applicable to strongly magnetized plasmas. Our model predicts sub-ion-scale reconnection rates significantly higher than those pertaining to large-scale reconnection, aligning with recent observations and simulations. We apply this reconnection model to the problem of inverse magnetic energy transfer at sub-ion scales. We derive time-dependent scaling laws for the magnetic energy decay and the typical magnetic structure dimensions that differ from those previously found in the MHD regime. These scaling laws are validated via two- and three-dimensional simulations, demonstrating that sub-ion scale magnetic fields can reach large, system-size scales via successive coalescence.