GRAVITATIONAL COLLAPSE OF MAGNETIZED CLOUDS. II. THE ROLE OF OHMIC DISSIPATION

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

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Author(s)

Detail(s)

Original languageEnglish
Pages (from-to)382-389
Journal / PublicationAstrophysical Journal
Volume647
Issue number1
Publication statusPublished - 10 Aug 2006
Externally publishedYes

Abstract

We formulate the problem of magnetic field dissipation during the accretion phase of low-mass star formation, and we carry out the first step of an iterative solution procedure by assuming that the gas is in free fall along radial field lines. This so-called "kinematic approximation" ignores the back reaction of the Lorentz force on the accretion flow. In quasi-steady state and assuming the resistivity coefficient to be spatially uniform, the problem is analytically soluble in terms of Legendre's polynomials and hypergeometric confluent functions. The dissipation of the magnetic field occurs inside a region of radius inversely proportional to the mass of the central star (the "Ohm radius"), where the magnetic field becomes asymptotically straight and uniform. In our solution the magnetic flux problem of star formation is avoided because the magnetic flux dragged in the accreting protostar is always zero. Our results imply that the effective resistivity of the infailing gas must be higher by at least 1 order of magnitude than the microscopic electric resistivity, to avoid conflict with measurements of paleomagnetism in meteorites and with the observed luminosity of regions of low-mass star formation.

Research Area(s)

  • ISM: clouds, ISM: magnetic fields, MHD, Planetary systems: protoplanetary disks, Stars: formation

Citation Format(s)

GRAVITATIONAL COLLAPSE OF MAGNETIZED CLOUDS. II. THE ROLE OF OHMIC DISSIPATION. / SHU, Frank H.; GALLI, Daniele; LlZANO, Susana; CAI, Mike.

In: Astrophysical Journal, Vol. 647, No. 1, 10.08.2006, p. 382-389.

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review