The Dynamics of the Interstellar Medium. I. Local Equilibrium.

Abstract

view Abstract Citations (170) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Dynamics of the Interstellar Medium. I. Local Equilibrium. Spitzer, Lyman, Jr. Abstract The physical properties of the interstellar medium, especially those which depend on the presence of small dust particles, are examined in detail. It is shown that if the electron density is as great as i~-~ per cm3 the charge on a dust particle will be determined by collisions with rapklly moving electrons rather than by photoelectric ionizations; a small particle will, in such a case, be charged to -2 volts, independently of its radius. Any deviations from equipartition of kinetic energy between all the inter- stellar particles will be reduced by l/e within at most ~ years if there is i proton per cm3, and within 4X ~ years if no ionized H is present but if i~-~ Ca~ ions per cm3 or their equivalent are assumed. The random velocities of dust particles should, therefore, be extremely small, and the mean free path should not be greater than a few astronomical units. The viscosity of the interstellar medium is evalu- ated and is shown to be negligible; in the neighborhood of stars whose random motion does not exceed 10 km/sec the medium will not acquire any net momentum. The rate of diffusion of interstellar parti- cles is also very low, and mixing of the various constituents in io9 years is restricted to a few parsecs Publication: The Astrophysical Journal Pub Date: May 1941 DOI: 10.1086/144273 Bibcode: 1941ApJ....93..369S full text sources ADS | Related Materials (2) Part 2: 1941ApJ....94..232S Part 3: 1942ApJ....95..329S