Ambipolar diffusion in selfgravitating isothermal layers
Abstract
Quasimagnetohydrostatic and local ionization equilibria are assumed in the present formulation and solution of the drift of magnetic field and ions embedded in a selfgravitating layer of neutral isothermal gas. The introduction of Lagrangian coordinates referred to the neutral gas allows this problem to be reduced to a nonlinear diffusion equation for the magnetic field, whose dimensionless form involves no parameters other than those introduced by the initial values. In the shapeinvariant solution, the magnetic field at each surface density point in the neutral fluid decays as the inverse square root of the elapsed time. Explicit estimates are given, as a function of the initial magnetic to neutral gas pressure in a natural family of cases, for the amount of time that must pass before the shapeinvariant solution becomes a good approximation for actual behavior. The results obtained are interpreted physically.
 Publication:

The Astrophysical Journal
 Pub Date:
 October 1983
 DOI:
 10.1086/161359
 Bibcode:
 1983ApJ...273..202S
 Keywords:

 Ambipolar Diffusion;
 Interstellar Magnetic Fields;
 Isothermal Layers;
 Nebulae;
 Space Plasmas;
 Lagrange Coordinates;
 Neutral Gases;
 Stellar Evolution;
 Astrophysics