Encyclopedia of Astrobiology

2011 Edition
| Editors: Muriel Gargaud, Ricardo Amils, José Cernicharo Quintanilla, Henderson James (Jim) CleavesII, William M. Irvine, Daniele L. Pinti, Michel Viso

Ambipolar Diffusion

Reference work entry
DOI: https://doi.org/10.1007/978-3-642-11274-4_59


Ambipolar diffusion is the slippage of neutral matter in a plasma with respect to an internal magnetic field. This slippage occurs when the ionization fraction is so low that collisions between neutral species and ions become relatively rare. At this point, the neutral atoms can move relative to the ions, which are effectively tied to the magnetic field. Ambipolar diffusion is thought to occur in molecular clouds, which are dense enough to shield much of the external, ionizing radiation. The cloud’s self-gravity can then cause the gas to condense, in spite of its internal magnetic field. This condensation ultimately leads to star formation.

See also

Copyright information

© Springer-Verlag Berlin Heidelberg 2011

Authors and Affiliations

  1. 1.Department of AstronomyUniversity of CaliforniaBerkeleyUSA