A Magnetothermodynamic Theory of Energy Transport In Collisionless Plasmas

Abstract

Presented here is an exploratory conceptual framework with the aim of describing electromagnetic and thermal energy transport and transfer in collisionless plasmas in a coherent way, starting from an arrow-of-time perspective. That is, arguments about the transport of energy are fundamentally based on the idea that systems tend to fill the phase space available to them. First, we describe electric fields, magnetic fields, and plasma particles as interacting subsystems that are thermodynamically linked in specific ways. Second, we discuss the importance of the stochastic electric field in the transport of plasma particles down energy density gradients until the energy flux contributions from so-called electrothermodynamic (ETD) interactions become sufficiently uniform. Third, the logic of ETD transport is extended to a magnetized system invoking 2 types of magnetothermodyamic (MTD) transport: 1) transport of electromagnetic energy through stochastic Poynting flux and 2) plasma energy transport through stochastic drift energy fluxes associated with local ExB drift motion. The magnitudes of the ETD and MTD mechanisms are tied to local characteristic scales of the electric field fluctuations and critical scales are derived beyond which ETD mechanisms dominate MTD mechanisms. Finally, we discuss the interplay between electrothermodynamic and magnetothermodynamic equilibria (ETE and MTE), dynamics in the small critical scale (MTD) limit, and the potential relevance of this type of description to the problem of reconnection onset and scale coupling.