Kinetic Verification of the Stochastic Ion Heating Mechanism in Collisionless Magnetic Reconnection

The origin of anomalous, non-classical ion heating during magnetic reconnection has been a longstanding problem. It is verified via fully kinetic analyses and particle-in-cell simulations that stochastic heating is the main ion heating mechanism in collisionless magnetic reconnection up to moderate guide fields. Strong in-plane Hall electric fields that form during reconnection render ion motions chaotic and de facto broaden the ion distribution function. The mechanism is consistent with numerous observed features of ion heating in reconnection, such as the preferential heating of ions with higher mass-to-charge ratios and the non-conservation of the ion magnetic moment.