Surface Wave Propagation in non--ideal plasmas

TL;DR

This paper investigates surface wave propagation in partially ionized, magnetized plasma slabs, highlighting the effects of nonideal MHD phenomena like Hall diffusion and the importance of fractional ionization.

Contribution

It introduces the impact of Hall diffusion and fractional ionization on surface wave characteristics in non-ideal plasmas, extending ideal MHD models.

Findings

Wave phase velocity increases slightly due to compressibility.

Waves below a certain cutoff frequency can propagate in Hall dominated regimes.

The cutoff frequency depends on fractional ionization more than plasma beta.

Abstract

The properties of surface waves in a partially ionized, compressible magnetized plasma slab are investigated in this work. The waves are affected by the nonideal magnetohydrodynamic effects which causes finite drift of the magnetic field in the medium. When the magnetic field drift is ignored, the characteristics of the wave propagation in a partially ionized plasma fluid is similar to the fully ionized ideal MHD except now the propagation properties depend on the fractional ionization as well as on the compressibility of the medium. The phase velocity of the sausage and kink waves increases marginally (by a few percent) due to the compressibility of the medium in both ideal as well as Hall diffusion dominated regimes. However, unlike ideal regime, only waves below certain cut off frequency can propagate in the medium in Hall dominated regime. This cut off for a thin slab has a weak dependence on the plasma beta whereas for thick slab no such dependence exists. More importantly, since the cut off is introduced by the Hall diffusion, the fractional ionization of the medium is more important than the plasma compressibility in determining such a cut off. We discuss the relevance of these results in the context of solar photosphere-chromosphere.