1) Applying equally to both positive and negative ions.
Fr.: diffusion ambipolaire
A physical process which allows a → molecular cloud to decouple from → interstellar magnetic field in order to undergo → gravitational collapse. A cloud of pure molecular gas would form stars very fast through collapse since neutral matter does not respond to the magnetic field. However, the magnetic field holds up a collapse because the ions present in the cloud collide with the neutrals and tie them to the field. The collapse can then only proceed if the magnetic field can be separated from the gas. In denser molecular cores the ionization degree decreases substantially and therefore neutrals and ions decouple.