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Astron. Astrophys. 351, 192-194 (1999)

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1. Introduction

Remnant magnetism of carbonaceous chondrite meteorites implies that the magnetic field where they formed had a strength of as much as 7 Gauss (Levy & Sonnett 1978). If a dynamo creates a field of such a strength in a protostellar disk, the disk may have a more tenuous corona with a magnetic field of comparable strength maintained by the convective transport and buoyant rise of flux tubes. Levy & Araki (1989) have suggested that such processes may have played rôles in the establishment of a corona around the protosolar disk. We identify conditions under which ambipolar diffusion, the relative motion of ions and neutrals driven by magnetic forces, occurs at a high enough speed to create around a protostellar disk an ionised region that is observable in recombination radiation.

In Sect. 2 we present calculations giving, as a function of density, the magnetic force per unit volume required for ambipolar diffusion to maintain a high fractional ionisation. Sect. 3 concerns recombination radiation detection limits.

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© European Southern Observatory (ESO) 1999

Online publication: November 2, 1999