Theory and numerical simulations of electron-only magnetic reconnection

Electron-only magnetic reconnection refers to reconnection events observed in the Earth's magnetosheath in which the ions appear to play no role; i.e., they occur at scales small enough that the ions are decoupled. Observations and numerical simulations report reconnection rates for these events that are significantly larger than the typical values associated with large-scale reconnection. In this work, we present an analytical model for electron-only reconnection applicable to strongly magnetized low beta plasmas. Our model predicts higher-than-conventional reconnection rates that primarily depend on the ratio between the ion Larmor radius and the size of the reconnecting structure. We validate this model via direct numerical simulations; and also propose an extension to plasma betas of order unity. Finally, we use this result to characterize the inverse cascade of magnetic energy via successive island coalescence at sub-ion scales.