Ambipolar Diffusion-Mediated Thermal Fronts in the Neutral ISM

Abstract

In a thermally bistable medium, cold, dense gas is separated from warm, rareified gas by thin phase transition layers, or fronts, in which heating, radiative cooling, thermal conduction, and convection of material are balanced. We calculate the steady-state structure of such fronts in the presence of magnetic fields, including the processes of ion-neutral drift and ion-neutral frictional heating. We find that ambipolar diffusion efficiently transports the magnetic field across the fronts, leading to a flat magnetic field strength profile. The thermal profiles of such fronts are not significantly different from those of unmagnetized fronts. The near uniformity of the magnetic field strength across a front is consistent with the flat field strength-gas density relation that is observed in diffuse interstellar gas.

17 pages, 12 figures, 1 table, accepted for publication in ApJ

References in corpus (3)

• Diffusion of magnetic field and removal of magnetic flux from clouds via turbulent reconnection
• Structure and Stability of Phase Transition Layers in the Interstellar Medium
• The Role of Ambipolar Diffusion in the Formation Process of Moderately Magnetized Diffuse Clouds

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