The Astrophysical Journal · 1983 · 46 citations · 0 references
The basic physics of untwisted flux tubes confined by an external plasma pressure has been developed by Parker (1979). However, observations indicate that in many situations on the sun flux tubes are twisted. There is, for instance, evidence for helical structures in erupting prominences. It is, therefore, important to extend the results already found for untwisted tubes to include the effects of twist. The present investigation is concerned with the structure of a thick twisted flux tube in an inhomogeneous atmosphere. Previous work on untwisted flux tubes and straight cylindrical twisted tubes is generalized, in order to describe the properties of twisted flux tubes confined by a varying external pressure. The governing equations are nonlinear, and, if the confining pressure is specified, they define a free surface problem. This problem is solved analytically in certain limiting cases, for which the complete structure of the field is found. Two exact solutions for force-free fields are studied in detail.