Micro-processes Driven by Shear Alfvén Waves Generating Parallel Potential Drop in the Auroral Plasma

University Of Alabama In Huntsville, Huntsville AL

Investigators

Abstract

Alfven waves are thought to play a significant role in the auroral particle acceleration process, but the plasma processes, which convert the Alfven wave energy into the electrostatic energy in a parallel potential drop (PPD), are still not fully understood. This project will continue a line of research in this topic that has used a two-fluid magnetohydrodynamic (MHD) model. In this two-fluid model the electric field parallel to the magnetic field lines is calculated from the electron momentum equation. The electron momentum equation includes linear and nonlinear inertial terms as well as an anomalous collision term. The anomalous collision term is an heuristic model of the electrostatic ion cyclotron (EIC) instability. The two-fluid model has been successful on a number of fronts, but these types of models are know to miss kinetic and microphysical processes such as (i) multi-streaming of charged particles and resulting micro-instabilities, (ii) plasma heating resulting in plasma evacuation and cavity formation, (iii) formation of micro-scale PPD like a double layer (DL) and (iv) effects of mirror force. The main thrust of this project will be to study the meso-scale propagation of shear Alfven waves (SAWs) using kinetic simulations that include the appropriate microphysics in a self-consistent way. The simulations will be done with a 2.5-dimensional particle-in-cell code. The primary focuses of attention for the project will be (i) the wave modes responsible for the anomalous resistivity, (ii) anomalous plasma heating resulting in cavity creation, (iii) cavity creation by nonlinear ponderomotive force, and (iv) double layer formation localizing E-parallel in cavities as seen in data from the FAST and Polar satellites. The research will determine the relative importance of double layers, anomalous resistivity, and mirror force in establishing the PPD in a propagating SAW, and will augment MHD and two-fluid MHD modeling efforts by providing rigorously determined expressions for the anomalous resistivity. The project will include research experience and support for a graduate student and undergraduate students. The parallelized kinetic code is used as a teaching tool for teaching parallel computing courses.