Equilibrium models for large stellar coronal loops

The properties of coronal loop structures with lengths comparable to or greater than a stellar radius are investigated for rapidly rotating lower main-sequence stars and in particular the young, active KO dwarf AB Doradus, which has a rotation period of 0.514 day. Numerical models are developed for static loops with constant cross-sectional area along their lengths, in thermal and hydrostatic equilibrium. As in previous work by other authors on solar loops, two classes of solution are found: 'hot' loops with temperature maxima at their summits, which are thermally stable, and 'cool' loops with temperature minima at their summits, which are unstable. The plasma temperatures and electron densities prevailing over most of the length of these large loops show excellent agreement with those estimated from X-ray observations of AB Dor. (author)