Hidden problems of thin-flux-tube approximation
Abstract
This paper scrutinizes the validity of the thin-flux-tube approximation for magnetic flux tubes embedded in a surrounding magnetic plasma. It is shown that the thin-flux-tube approximation gives an accurate description of surface waves for CT2> CAe2, body waves for C_Te2> CT2 and surface leaky waves for CTe2< CT2 < CAe2. The Leibovich-Roberts equation for nonlinear surface waves in a flux tube embedded in a field free plasma is generalized to a flux tube immersed in a magnetic plasma. The generalized Leibovich-Roberts (GLR) equation describes the propagation of nonlinear slow surface, body and surface leaky waves in tubes. The shortcomings of the GLR equation are discussed. The Korteweg-de Vries equation (KdV) is generalized for surface waves. The advantage of the second order thin-flux-tube approximation is shown. Two scenarios for the heating of coronal loops are discussed. It is emphasized, that the application of the thin-flux-tube approximation to thin tubes of non-zero diameter has to take into account possible wave emission by the tube and shock front formation for amplitudes in excess of some critical value.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- October 2001
- DOI:
- 10.1051/0004-6361:20011094
- Bibcode:
- 2001A&A...377..330Z
- Keywords:
-
- AGNETOHYDRODYNAMICS (MHD);
- WAVES;
- SUN: CORONA;
- OSCILLATIONS