Publications Details

Analytic comparison of the dispersion relation of waves present in various MHD models

Alcala, Daniel

Ideal magnetohydrodynamics (MHD) has been a widely used theoretical model for studying fusion plasmas. However, as it is well known, MHD is not an entirely accurate physical model and, in some cases, can miss essential physics that is of interest. To remedy this, several improved MHD models have been proposed; these include Hall MHD and a recently developed extended-MHD model. For these models, it is important to understand the predicted plasma responses to infinitesimal perturbations; that is, their relevant wave dynamics. In this work, I derive the wave dispersion relations for ideal, Hall, and extended MHD models and compare them to those obtained using the two-fluid model for plasmas. It is shown that, for waves with frequencies below or close to the ion gyrofrequency, Hall MHD and extended MHD reproduce quite accurately the wave dispersion relations. However, as it is expected, at higher wave frequencies, all MHD models diverge from the results predicted using the two-fluid model.