On local and non-local energy transfers in Hall magnetohydrodynamic turbulence

Abstract

A systematic study of inertial energy cascade in three-dimensional Hall magnetohydrodynamic turbulence is conducted to probe into the locality of energy conserving triads and the subsequent transfers. Using direct numerical simulations, we calculate the shell-to-shell energy transfer rates corresponding to b-to-b (magnetic to magnetic) and j-to-b (current to magnetic) channels due to the Hall term, and convincingly show that both channels comprise of a combination of local and non-local energy transfers. A local inverse transfer is consistently observed at all scales of the b-to-b channel whereas for the j-to-b channel, the transfer due to local interactions shows a transition from a weak inverse to a strong direct cascade across the Hall scale. Calculating mediator-specific transfer rates, we also conclude that a considerable amount of local energy transfer is mediated by the non-local triads, especially at small-scales of j-to-b transfer. Assuming power-laws for the modal fields, we offer heuristic arguments for some of our observed results. The present study captures the intricate dynamics of energy transfer due to the Hall term and hence can be used to develop more insightful analytical models (shell models for example) for Hall magnetohydrodynamic cascade and to carefully segregate the local and the non-local heating in the space plasmas.