Astrophysics and Plasma Physics of Solar Wind Origins
Igor Veselovsky - Skobeltsyn Institute of Nuclear Physics, Moscow
June 01,2010
Why does the solar wind blow? When and how did it start to blow? What are the main energy and momentum sources of the solar wind?
The spherically symmetric model of the quasi-steady flow in the stellar atmospheres (Bondi, 1952) is very simple and physically
transparent for analytical considerations. Three admissible types of solutions of the governing Bernoulli equation are available
in this model: (1) static v=0, (2) expanding wind type flow v>0, (3) contracting accretion type flow v<0. The selection between them depends
on the imposed internal and external boundary conditions. This means that the solar wind origin problem cannot be properly addressed nor
completely explained in the framework of this model alone without additional assumptions. More appropriate and complicated non-steady state
and inhomogeneous models are not well developed. Nevertheless, the Bondi model is useful for the demonstration of the necessity of
the time dependent approach for obtaining a physically correct answer to the long standing question: why does the solar wind blow?
It is not only because of the instantaneous hot corona and rarefied interstellar medium around the Sun, as often correctly assumed
(Parker, 1957), but also because of the evolutionary state of our star and its magnetic activity. Magnetic stresses dominate in
coronal holes and coronal mass ejections. Solar-like stars of the same type as the Sun can exist with a hot corona and situated in
a rarefied interstellar medium, but without any wind or even in the accretion state because of magnetic forces. The existence of
such stars (acceptors) is not prohibited by any physical laws and could be searched in UV line Doppler shift measurements as well as
of other stars similar to the Sun in this respect (donors). The role of rotation, convection, and radiation transports is also discussed.
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