Closed and open magnetic fields in stellar winds
Abstract
A 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.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 1983
- DOI:
- 10.1086/160830
- Bibcode:
- 1983ApJ...266..823M
- Keywords:
-
- Giant Stars;
- Magnetic Field Configurations;
- Solar Magnetic Field;
- Stellar Coronas;
- Stellar Magnetic Fields;
- Stellar Winds;
- Hertzsprung-Russell Diagram;
- Magnetohydrodynamic Flow;
- Plasma Interactions;
- Stellar Mass Ejection;
- Stellar Temperature;
- X Ray Astronomy;
- Astrophysics