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Heating and Momentum Deposition in Hot Stars

Published online by Cambridge University Press:  30 March 2016

J.I. Castor
J.I. Castor*
Affiliation:
Lawrence Livermore National LaboratoryBox 808, Livermore, CA 94550, U.S.A.

Extract

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The one great point of similarity between the coronae of hot and cool stars is that both are spatially extended regions of more-or-less tenuous gas that is flowing outward, and at least some of which is at a temperature in excess of 106 K. Coronae defined in this way are almost universal among stars—excepting cool supergiants—but this similarity may hide significant differences in the processes that produce coronae. There are two rather different paradigms for their origin: the cool-star paradigm and the hot star paradigm.

The coronae of cool stars like the sun are of such a low density that radiative cooling is inefficient; the outward flow is weak enough that there is a fairly extended subsonic flow region. The outer corona is heated by a flux of wave energy, and some of this energy is then conducted inward to heat the inner corona. The outflow is driven by the pressure of the heated gas, assisted perhaps by wave pressure. The structure of the corona is greatly affected by the topology of the magnetic field, which channels the outflow and governs the transport of energy and momentum by waves.

Type
Joint Commission Meetings
Information
Highlights of Astronomy , Volume 9: Highlights of Astronomy. As presented at the XXIst General Assembly of the IAU, 1991 , 1992 , pp. 649 - 650
Copyright
Copyright © Kluwer 1992

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