5 - Waves in the magnetised solar atmosphere

Summary

Oscillations and waves in the quiet and active solar atmosphere constitute a zoo of distinct and overlapping phenomena: internetwork oscillations, K-grains, running penumbral waves, umbral oscillations, umbral flashes etc. The distinctive oscillation spectra associated with the network, the internetwork, and sunspots and pores are a strong indicator that the magnetic field has a significant dynamical effect on wave motions. This immediately raises two questions i) Can waves be used as diagnostic indicators of the magnetic field? and ii) Do the different properties of wave motions in various field geometries have consequences for the efficiency of wave-heating in the atmosphere and corona? I will discuss some new numerical calculations of wave propagation in a variety of model atmospheres, which throw some light on these questions.

Introduction

The field of helioseismology has shown how waves which propagate through the deep solar interior can be used to determine the internal properties of the Sun – including its stratification, differential rotation, and sub-surface flow fields. Given the wide variety of waves and oscillations observed in the atmosphere of the Sun, in both Quiet and Active Regions, it is natural to ask whether the structures of these regions can also be determined from a wave analysis.

However, a brief consideration of the problem indicates that there are a number of critical differences between the atmospheric-wave problem and the p-mode problem which make the former vastly more difficult to study.