Oscillatory Modes of a Prominence-PCTR-Corona Slab Model

TL;DR

This paper investigates the magnetoacoustic oscillations in a prominence-corona slab model, revealing how different regions influence wave modes and identifying new solutions introduced by the prominence-corona transition region.

Contribution

It provides a detailed classification of magnetoacoustic modes in a prominence slab, including the effects of the transition region, which were not previously analyzed.

Findings

Fast modes are dominated by prominence conditions for observed wavelengths.

The inclusion of the PCTR introduces new slow modes without significantly changing existing mode frequencies.

Internal and external slow modes are governed by prominence and coronal properties, respectively.

Abstract

Oscillations of magnetic structures in the solar corona have often been interpreted in terms of magnetohydrodynamic waves. We study the adiabatic magnetoacoustic modes of a prominence plasma slab with a uniform longitudinal magnetic field, surrounded by a prominence-corona transition region (PCTR) and a coronal medium. Considering linear small-amplitude oscillations, the dispersion relation for the magnetoacoustic slow and fast modes is deduced assuming evanescent-like perturbations in the coronal medium. In the system without PCTR, a classification of the oscillatory modes according to the polarisation of their eigenfunctions is made in order to distinguish modes with fast-like or slow-like properties. Internal and external slow modes are governed by the prominence and coronal properties respectively, and fast modes are mostly dominated by prominence conditions for the observed wavelengths. In addition, the inclusion of an isothermal PCTR does not substantially influence the mode frequencies, but new solutions (PCTR slow modes) are present.