Fast Ion Heating in Transient Collisionless Magnetic Reconnection via an Intrinsic Stochastic Mechanism

Stochastic heating has been known to be a powerful ion heating mechanism in the solar wind, atmosphere, and flares. In this Letter, we show that stochastic ion heating is inherent to transient collisionless magnetic reconnection. The explanation exploits the connected nature of electron canonical vorticity to show analytically that the in-plane electric and magnetic fields in a typical reconnection geometry satisfy the condition for stochastic heating of ions. Electron fluid simulations, test ion simulations, and comparisons to experiments all support the existence of this mechanism.