Three-dimensional models of a galactic wind expansion with ellipsoidal geometry. I - The hydrodynamical test case

The outflow of gases from coronal regions of galaxies is mathematically discussed. A new model for modeling galactic wind expansion in three dimensions by the use of ellipsoidal coordinates is formulated. The model gives a reasonable description of the actual quasi-ellipsoidal geometry of many galaxies, and also allows for a study of the transition from planar to spherical models which appear as the asymptotic cases of an infinitely flattened ellipsoid and an ellipsoid with three equal-principal axes, respectively. The model also permits the variation of the galactic wind properties as functions of the direction to be investigated. As an example, the method is applied to realistic galactic wind systems including MHD flows. 60 refs