Particle‐fluid simulation of the auroral current circuit

Abstract

The incompatibility between stationary kinetic and dynamic fluid descriptions of auroral electron acceleration has been an outstanding problem in space physics for decades. In this study we introduce a new numerical simulation model that provides a unified picture by including electron temperature variations consistent with collisionless kinetic theory in the fluid description. We demonstrate that this new particle‐fluid model can describe the partial reflection of Alfvén waves from the acceleration region, as well as the formation of a field‐aligned potential drop proportional to the upward current. This study also suggests that for example ion dynamics and high‐frequency waves must be added to the model before it properly can describe the return current region. Simulations based on the particle‐fluid concept can be applied to various processes in space physics and astrophysics where strong currents flowing along an inhomogeneous magnetic field will cause temperature increases and field‐aligned electric fields.