The book is the first monograph in the Soviet literature, reflecting the current state of the hydrodynamic theory of interplanetary plasma, circumstellar gas and its influence on the interstellar medium. Special Section on the Spiral Structure of Galaxies . Based on rich experimental material, obtained during the study of outer space with the help of interplanetary stations and satellites , and the results of modern theoretical studies, the authors tried to build a complete picture of gas dynamics processes , which occur in the solar wind , in the interstellar medium , in the galaxies. The book is intended for readers working in the field of astrophysics, magnetic hydrodynamics, plasma physics, gas dynamics.