Stellar winds
Date
1971
Authors
Murch, Martin Robert
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Abstract
The phenomenon of mass loss from stars is surveyed. It is shown to be of widespread occurrence and, in many cases, to be of sufficient magnitude to alter significantly the course of stellar evolution. A considerable number of different mechanisms appear to be responsible for mass ejection; from these the thermally driven mechanism, believed to be responsible for the solar wind, is chosen for detailed investigation.
The observed characteristics of the solar corona and solar wind are reviewed, and the observational results are used to show, by means of kinetic theory, that the solar wind flow is most appropriately treated by means of hydrodynamics.
Solutions of the hydrodynamic equations are obtained on the assumptions that the only heating effect above the base of the corona is due to thermal conduction, and that the thermal conduction flux tends to zero at infinite distances from the star.
Models corresponding to the solar wind are produced which indicate a rate of mass loss from the sun of about 3.3 x 10⁻¹⁴ M☉/year, in reasonable agreement with space flight observations. There are indications that the non-thermal heating mechanisms responsible for the high coronal temperatures extend for a considerable distance into the solar wind.
Empirical relationships deduced from these models indicate that thermally driven stellar winds from hot, dense coronas may be capable of causing quite considerable rates of mass loss.