Dynamics of fast and slow magnetoacoustic waves in plasma slabs with thermal misbalance

TL;DR

This study investigates how thermal misbalance and non-uniformity influence the behavior of magnetoacoustic waves in solar plasma slabs, revealing differential effects on slow and fast wave phase speeds and dissipation, with implications for plasma diagnostics.

Contribution

The paper derives new dispersion relations for magnetoacoustic waves in thermally active plasma slabs considering non-uniformity and thermal misbalance, highlighting their impact on wave dynamics.

Findings

Slow wave phase speed is highly affected by thermal misbalance at long wavelengths.

Fast wave phase speed remains largely unaffected by thermal misbalance.

Dissipation of slow waves is stronger than that of fast waves in coronal conditions.

Abstract

Non-uniformity of the solar atmosphere along with the presence of non-adiabatic processes such as radiation cooling and unspecified heating can significantly affect the dynamics and properties of magnetoacoustic (MA) waves. To address the co-influence of these factors on the dispersion properties of MA waves, we considered a single magnetic slab composed of the thermally active plasma. Using the perturbation theory, we obtained a differential equation that determines the dynamics of the two-dimensional perturbations. Applying the assumption of strong magnetic structuring, we derived the dispersion relations for the sausage and kink MA modes. The numerical solution of the dispersion relations for the coronal conditions was performed to investigate the interplay between the non-uniformity and the thermal misbalance. For the heating scenario considered, it was obtained that the phase speed of both the sausage and kink slow MA waves is highly affected by the thermal misbalance in the long wavelength limit. The obtained characteristic timescales of the slow waves dissipation coincide with the periods of waves observed in the corona. Simultaneously, the phase speed of the fast waves is not affected by the thermal misbalance. The geometry of the magnetic structure still remains the main dispersion mechanism for the fast waves. Our estimation reveals that dissipation of the fast waves is weaker than dissipation of the slow waves in the coronal conditions. The obtained results are of importance for using the magnetoacoustic waves not only as a tool for estimating plasma parameters, but also as a tool for estimating the non-adiabatic processes.