Flow generation via catastrophic loss of equilibrium in weakly rotating self-gravitating fluids: A minimal idealized model.

Abstract

This paper explores the catastrophic energy transformations, in particular the ones leading to the generation of a flow in a weakly rotating self-gravitating fluid/gas found, for instance, in the vicinity of a massive compact object. Because of the similarity in the governing equations, the system dynamics is worked out exactly in parallel to the methods developed for investigating catastrophic relaxation in stellar plasmas [S. Ohsaki et al., Astrophys. J. 559, L61 (2001)0004637X10.1086/323651; Astrophys. J. 570, 395 (2002)0004-637X10.1086/339499; E. Saralidze et al., Astrophys. Space Sci. 370, 64 (2025)10.1007/s10509-025-04456-1]. In the latter, a more "complex" equilibrium state, on slow changes in the environment, can lose its equilibrium (catastrophe), and transform to a less complex state with a very different energy mix from the original. It is shown that a similar transformation in the weakly rotating self-gravitating fluid/gas will convert much of its gravitation energy into kinetic energy in the flow. Since flows are a perennial ingredient of high-energy astrophysical systems, the energy transformation processes revealed in the present study, can advance our understanding of a variety of them. Some particularly relevant examples are macroscale flows / structures in galaxies, accretion discs, and the dynamics and stability of a rotating star / its atmosphere.