The structure and energy balance of cool star atmosphere.
Abstract
The atmospheric structure and energy balance phenomena associated with magnetic fields in the Sun are reviewed and it is shown that similar phenomena occur in cool stars. The evidence for the weakening or disappearance of transition regions and coronae is discussed together with the appearance of extended cool chromospheres with large mass loss, near V-R = 0.80 in the H-R diagram. Like the solar atmosphere, these atmospheres are not homogeneous and there is considerable evidence for plage regions with bright TR emission lines that overlie dark (presumably magnetic) star spots. The IUE observations are providing important information on the energy balance in these atmospheres that should guide theoretical calculations of the nonradiative heating rate. Recent high dispersion spectra are providing unique information concerning which components of close binary systems are the dominant contributors to the observed emission. A recent unanticipated discovery is that the transition lines are redshifted (an antiwind) in DRa (G2 Ib) and perhaps other stars. Finally, the G and K giants and supergiants are classified into three groups depending on whether their atmospheres are dominated by closed magnetic flux tubes, open field geometries, or a predominately open geometry with a few closed flux tubes embedded.
- Publication:
-
NASA Conference Publication
- Pub Date:
- 1982
- Bibcode:
- 1982NASCP2238...17L
- Keywords:
-
- Astronomy;
- Giant Stars;
- Stellar Atmospheres;
- Stellar Magnetic Fields;
- Supergiant Stars;
- Ultraviolet Astronomy;
- Astronomical Spectroscopy;
- Binary Stars;
- Cool Stars;
- Dwarf Stars;
- G Stars;
- Iue;
- K Stars;
- Solar Physics;
- Stellar Spectra;
- Stellar Winds;
- Atmospheres:Cool Stars;
- Cool Stars:Magnetic Fields;
- Solar Magnetic Fields