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closed and open magnetic fields in stellar windsA numerical study of the interaction between a thermal wind and a global dipole field in the sun and in a giant star is reported. In order for closed field lines to persist near the equator (where a helmet-streamer-like configuration appears), the coronal temperature must be less than a critical value Tc, which scales as M/R. This condition is found to be equivalent to the following: for a static helmet streamer to persist, the sonic point above the helmet must not approach closer to the star than 2.2-2.6 stellar radii. Implications for rapid mass loss and X-ray emission from cool giants are pointed out. The results strengthen the case for identifying empirical dividing lines in the H-R diagram with a magnetic topology transition locus (MTTL). Support for the MTTL concept is also provided by considerations of the breakdown of magnetostatic equilibrium.
Document ID
19830045173
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Mullan, D. J.
(Franklin Institute, Bartol Research Foundation, Newark DE, United States)
Steinolfson, R. S.
(California, University Irvine, CA, United States)
Date Acquired
August 11, 2013
Publication Date
March 15, 1983
Publication Information
Publication: Astrophysical Journal
Subject Category
ASTROPHYSICS
Funding Number(s)
CONTRACT_GRANT: NOAA-NA-80RAD00012
CONTRACT_GRANT: NSF ATM-78-20936-01
CONTRACT_GRANT: NAGW-93
CONTRACT_GRANT: NAGW-5
Distribution Limits
Public
Copyright
Other