Waves in a warm, ideal two-fluid plasma and model applications
Date:
Poster presentation at EPS 2021, virtual.
Abstract. Waves in a warm, magnetised, ideal two-fluid plasma, consisting of electrons and ions, are described by a general, polynomial dispersion relation (see e.g. Goedbloed, Keppens & Poedts, 2019). The 6 wave types occur in forward-backward propagating pairs and are labelled S, A, F, M, O, and X, as introduced by Keppens and Goedbloed (2019). Using the angle between the direction of propagation and the background magnetic field, it is argued that parallel and perpendicular propagation exhibit unique behaviour. The factorisation of the dispersion relation at parallel and perpendicular propagation allows for mode crossings, whilst the lack of factorisation at oblique angles results in avoided crossings and thus a frequency ordering. Exploiting the general nature of the dispersion relation, phase and group speed diagrams can be computed at arbitrary wavelengths, further highlightning this behaviour. The general nature of the dispersion relation also lends itself to various applications. In various different limits we can obtain e.g. a low-frequency wave description, Hall MHD, a generalisation of the Appleton-Hartree equation including the thermal electron velocity and approximations of whistler behaviour. Whilst some literature results are recovered, others can be significantly expanded, such as the wide variety of whistling behaviours occurring across all 6 wave types at all angles.