Magnetic Flux Transport in the ISM through Turbulent Ambipolar Diffusion
Under ideal MHD conditions the magnetic field strength should be correlated with density in the interstellar medium (ISM). However, observations indicate that this correlation is weaker than expected. Ambipolar diffusion can decrease the flux-to-mass ratio in weakly ionized media; however, it is generally thought to be too slow to play a significant role in the ISM except in the densest molecular clouds. Turbulence is often invoked in other astrophysical problems to increase transport rates above the (very slow) diffusive values. Building on analytical studies, we test with numerical models whether turbulence can enhance the ambipolar diffusion rate sufficiently to explain the observed weak correlations. The numerical method is based on a gas-kinetic scheme with very low numerical diffusivity, thus allowing us to separate numerical and physical diffusion effects.
KeywordsISM MHD ambipolar diffusion turbulence
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- Ballesteros-Paredes, J., Vâzquez-Semadeni, E. and Scalo, J.: 1999, Api 515, 286. Bourke, T.L., Myers, P.C., Robinson, G. and Hyland, A.R.: 2001, ApJ 554, 916.Google Scholar
- Heiles, C.: 2003, Observations of Turbulence in the Diffuse ISM, Proceedings of the Workshop: Magnetic Fields and Star Formation: Theory Versus Observations,Kluwer.Google Scholar
- Heitsch, F., Zweibel, E.G., Slyz, A.D. and Devriendt, J.E.G.: 2003, in preparation.Google Scholar
- Mestel, L.: 1985, in: D.C. Black and M.S. (eds.), Protostars and Planes II, Matthews Tucson: Univ. Arizona Press, 320.Google Scholar
- Petschek, A.G.: 1969, in: W.N. Hess (ed.), AAS-NASA Symp. on the Physics of Solar Flares, NASA SP-50, Greenbelt: NASA, p. 425.Google Scholar
- Troland, T.H. and Heiles, C.: 1986, ApJ 339, 345.Google Scholar