Hydrodynamic instabilities in the models of the formation of young stellar objects

The features of unstable motions in the regions of active star formation are considered. The purpose of the research is to determine the magnitude and scale of inhomogeneities for which the Jeans gravitational compression criterion is satisfied. Mathematical models are used that take into account nonequilibrium radiation processes and self-gravity. The results of calculations of the cumulation of mass during the propagation of the ionization-shock front in the cloud are presented; a qualitative agreement is established between the motion structure and the one obtained on the basis of the thin layer model Cherny. In the case of Richtmyer -Meshkov instability it was found that density perturbations increase significantly due to radiation cooling. Taking into account the gravitational interaction between particles of the accelerating moving gas layer, a criterion is formulated for the dominant influence of self-gravity on the shape of inhomogeneities compared with the Rayleigh -Taylor instability. Morphologically, heterogeneities of various origins differ little and are observed mainly on the inner side of the ionization-shock front, facing the radiation source. The authors of this work for the first time found that gas-dynamic phenomena at the outer boundary of a layer compressed by a shock wave can reflect the presence of condensations that existed in the interstellar medium before the passage of the ionizationshock front. Computer modeling has shown that when a condensation (cloud, clot) penetrates into an accelerating moving layer, the formation of a cumulative jet occurs. The effect of acceleration, gas densities in the layer and in the cloud, and the shape of the cloud on the manifestation of the cumulative effect is investigated.