The influence of magnetic fields on radiative damping of magnetoatmospheric oscillations

Abstract

We examine the non adiabatic effects on the modes of an isothermal stratified magnetic atmosphere. The present investigation is a continuation of earlier work by Banerjee, Hasan & Christensen-Dalsgaard (1995, 1996, 1997), where the interaction of various elementary modes in a stratified magnetised atmosphere was studied in the purely adiabatic limit. The inclusion of radiative dissipation in magnetoatmospheric wave problem - even in the over simplified Newtonian Cooling approximation - is of great importance. Including Newtonian Cooling, in the weak field limit, an analytic expression for the dispersion relation is derived which allows the effect of weak magnetic field on the modes to be studied. We examine the nature of the eigen frequency curves in the diagnostic diagram and find that, similar to the previous analysis, the modes undergo avoided crossings. We study the full frequency spectrum and the interaction amongst various modes. Strong mode coupling in the avoided crossing regions permits energy leakage. Our results, find application in the analysis of waves in flux-tubes on the Sun. We study the influence of magnetoatmospheric waves on spectral line profiles.