Waves in the Hall-magnetohydrodynamics model

Abstract

The three magnetohydrodynamic (MHD) waves are followed as they transition under the influence of an increasingly strong Hall current effect to the characteristic waves of the Hall-MHD model. Also followed are the wave normal surfaces and the ray surfaces (approximating wave fronts) of these waves. The changes in the nature of the waves are found to be considerable, and are described both analytically and numerically. Most notably, the incompressible MHD shear Alfvén wave becomes a compressible fluid-dynamical wave with negligible perturbation of the electromagnetic field, while the two MHD compressible waves become incompressible, the fast wave becoming mostly electromagnetic and the slow wave becoming mostly fluid-dynamical.