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Dust-driven Dynamos in Accretion Disks

Bellan, P. M. (2008) Dust-driven Dynamos in Accretion Disks. Astrophysical Journal, 687 (1). pp. 311-339. ISSN 0004-637X. doi:10.1086/591244.

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Magnetically driven astrophysical jets are related to accretion and involve toroidal magnetic field pressure inflating poloidal magnetic field flux surfaces. Examination of particle motion in combined gravitational and magnetic fields shows that these astrophysical jet toroidal and poloidal magnetic fields can be powered by the gravitational energy liberated by accreting dust grains that have become positively charged by emitting photo-electrons. Because a dust grain experiences magnetic forces after becoming charged, but not before, charging can cause irreversible trapping of the grain, so dust accretion is a consequence of charging. Furthermore, charging causes canonical angular momentum to replace mechanical angular momentum as the relevant constant of the motion. The resulting effective potential has three distinct classes of accreting particles distinguished by canonical angular momentum, namely (1) "cyclotron-orbit," (2) "Speiser-orbit," and (3) "zero canonical angular momentum" particles. Electrons and ions are of class 1, but depending on mass and initial orbit inclination, dust grains can be of any class. Light-weight dust grains develop class 1 orbits such that the grains are confined to nested poloidal flux surfaces, whereas grains with a critical weight such that they experience comparable gravitational and magnetic forces can develop class 2 or class 3 orbits, respectively producing poloidal and toroidal field dynamos.

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Bellan, P. M.0000-0002-0886-8782
Additional Information:© 2008. The American Astronomical Society. Received 2008 April 16; accepted 2008 June 20; published 2008 November 1. Print publication: Issue 1 (2008 November 1).
Subject Keywords:accretion, accretion disks; circumstellar matter; dust, extinction; magnetic fields; ISM: jets and outflows; MHD
Issue or Number:1
Record Number:CaltechAUTHORS:BELapj08b
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:13085
Deposited By: Archive Administrator
Deposited On:17 Jan 2009 04:42
Last Modified:08 Nov 2021 22:35

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