Eine Methode zur Berechnung dreidimensionaler Störungen an Polytropenmodellen

In model calculations regarding the axisymmetrical collapse of rotating interstellar gas clouds, stationary ring structures have been obtained. Information regarding the stability of such structures is important. Studies of nonaxisymmetrical perturbations in the case of rotating isothermal gas clouds have been conducted with the aid of three-dimensional hydrodynamic codes. However, the employed procedure has the disadvantage of limited resolution. The exact study of the stability of a quasi-stationary model requires a program, based on a linear perturbation theory, which can be employed after each time step at the calculation of the equilibrium model. A suitable numerical method is considered, and first test calculations involving a polytropic model with polytropic index five are discussed.