Static Equilibria of the Interstellar Gas in the Presence of Magnetic and Gravitational Fields: Large-Scale Condensations

Abstract

view Abstract Citations (131) References (14) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Static Equilibria of the Interstellar Gas in the Presence of Magnetic and Gravitational Fields: Large-Scale Condensations Mouschovias, Telemachos Ch. Abstract We present equilibrium states of the interstellar gas, which has run down the perturbed magnetic field lines of a stratified, isothermal initial state under the action of a vertical galactic gravitational field. The final states are lower in total energy than the corresponding initial states. Their properties depend quantitatively on the horizontal (but not so much on the vertical) wavelength of the initial perturbation. A striking feature of the final states is that the scale height of the gas increases (decreases) where the gas density increases (decreases). A connection between initial and final states is made by conserving the mass-to-flux ratio in each flux tube. Thus, although we determine final equilibrium states by solving a time-independent problem, in a time-dependent problem our final states can be reached from the corresponding initial states through continuous deformations of the field lines. The final states are consistent with observations in the solar neighborhood. We treat the interesting case of the magnetic pressure being initially comparable to the pressure of the thermal gas. We show that the isothermal gas-field-gravity system possesses an "energy integral." An effective potential energy is identified, and an "energy principle" follows as a corollary. The iterative procedure used in order to solve the magnetohydrostatic equations is outlined, and upper limits on the numerical errors are given. We also extend our formalism so that it can apply to the case of a general (rather than an isothermal) equation of state. Subject headings: hydromagnetics - instabilities - interstellar matter - magnetic fields - plasmas Publication: The Astrophysical Journal Pub Date: August 1974 DOI: 10.1086/153032 Bibcode: 1974ApJ...192...37M full text sources ADS |