Linear and nonlinear magnetohydrodynamic waves in twisted magnetic flux tubes

Dynamics of axisymmetric Alfven and slow magnetoacoustic waves in weakly tw isted magnetic flux tubes is considered. Linear dispersion relations for th e waves are derived and analyzed in the presence of the twisting. The weakl y nonlinear dynamics is shown to be governed by the Korteweg-de Vries equat ion. Nonlinear slow body waves appear as a narrowing of tube in a low beta plasma and widening of tube, when beta >> 1. Nonlinear Alfven torsional wav es appear as a widening (beta > 1) and narrowing (beta < 1) of tube, accomp anied by the local increase of the tube twisting. (C) 1999 Published by Els evier Science B.V.