Wave propagation in a magnetic cylinder

TLDR: In this article, the authors investigated the nature of oscillations in a magnetic cylinder embedded in magnetic environment and showed that the standard slender flux tube analysis of a kink mode in a cylinder excludes the possibility of a second mode, which arises under photospheric conditions.

Abstract: The nature of oscillations in a magnetic cylinder embedded in a magnetic environment is investigated. It is shown that the standard slender flux tube analysis of a kink mode in a cylinder excludes the possibility of a second mode, which arises under photospheric conditions. Under coronal conditions, two widely separated classes of oscillation can be freely sustained, one on an acoustic time-scale and the other on an Alfvenic time-scale. The acoustic-type oscillations are always present, but the much shorter period, Alfvenic-type, oscillations arise only in high density (strictly, low Alfven velocity) loops. An application to waves in fibrils is also given, and suggests (following Wentzel, 1979) that they are fast kink waves propagating in a density enhancement.