Dissipative-free models for wave dynamics of interstellar gas-dust medium in Galactic magnetic fields

Abstract

Current study of interstellar gas dynamics leads to the conclusion that large scale motions are dominated by strong coupling between gas-dust flows and Galactic magnetic fields: the widths of molecular lines is a direct evidence for such motions. However the absence of reliable information regarding microscopic composition and electrodynamical properties of interstellar matter can cause serious difficulties for an unambiguous theoretical interpretation of observable motions. We accentuate this uncertainty by three alternative models of dissipative-free wave motions owing their origin to the presence of uniform magnetic field. To wit. (i) the hydromagnetic waves in a non-magnetic perfectly conducting medium. (ii) the magneto-elastic waves in a non-conducting highly paramagnetic medium and (iii) whistlers - spiral magneto-electror waves. Emphasis is laid on two last wave processes, fairly fresh to interstellar gas dynamics, which are discussed in juxtaposition with well-studied hydromagnetic Alfvénic waves.