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Astron. Astrophys. 341, 936-942 (1999)

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A semi-analytical model of disk evaporation by thermal conduction

C.P. Dullemond

Leiden Observatory, P.O. Box 9513, 2300 RA Leiden, The Netherlands

Received 14 April 1998 / Accepted 28 September 1998


The conditions for disk evaporation by electron thermal conduction are examined, using a simplified semi-analytical 1-D model. The model is based on the mechanism proposed by Meyer & Meyer-Hofmeister (1994) in which an advection dominated accretion flow evaporates the top layers from the underlying disk by thermal conduction. The evaporation rate is calculated as a function of the density of the advective flow, and an analysis is made of the time scales and length scales of the dynamics of the advective flow. It is shown that evaporation can only completely destroy the disk if the conductive length scale is of the order of the radius. This implies that radial conduction is an essential factor in the evaporation process. The heat required for evaporation is in fact produced at small radii and transported radially towards the evaporation region.

Key words: hydrodynamics – black hole physics – accretion, accretion disks

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© European Southern Observatory (ESO) 1999

Online publication: December 16, 1998