Oscillatory motions in intense flux tubes

The detailed nature of oscillatory motions in intense flux tubes is examined. States of constant β (the ratio of gas to magnetic pressure) are considered, and the character of motions that can occur in such tubes is analysed. Heat exchange between the tube and the ambient medium is included using Newton's law of cooling. Adopting a linear analysis, results for both polytropic and real atmospheres are presented. In the latter case, a height dependent radiation exchange time constant is used. For purposes of comparison with earlier studies, results for the adiabatic case are also given. Growth rates, oscillation frequencies and eigenvectors of the fundamental modes are calculated for different values of the initial magnetic field strength. (author)