Perpendicular ion heating in turbulence and reconnection: magnetic moment breaking by coherent fluctuations

We study the interaction of an ion with a fluctuation in the electromagnetic fields that is localised in both space and time. We study the scale dependence of the interaction in both space and time, deriving a generic form for the ion’s energy change, which involves an exponential cutoff based on the characteristic time scale of the electromagnetic fluctuation. This leads to diffusion in energy in both v_⊥ and v_∥ . We show how to apply our results to general plasma physics phenomena, and specifically to Alfvénic turbulence and to reconnection. Our theory can be viewed as a unification of previous models of stochastic ion heating, cyclotron heating and reconnection heating in a single theoretical framework.