Definition and empirical structure of the range of stellar chromospheres-coronae across the H-R diagram: cool stars

Technical Report · Mon Sep 01 04:00:00 EDT 1986

OSTI ID:6932190

Linsky, J L

Major advances in our understanding of non-radiative heating and other activity in stars cooler than T sub eff = 10,000K has occured in the last few years. This observational evidence is reviewed and the trends that are now becoming apparent are discussed. The evidence for non-radiatively heated outer atmospheric layers (chromospheres, transition regions, and coronae) in dwarf stars cooler than spectral type A7, in F and G giants, pre-main sequence stars, and close bindary systems is unambiguous, as is the evidence for chromospheres in the K and M giants and supergiants. The existence of non-radiative heating in the outer layers of the A stars remains undetermined despite repeated searches at all wavelengths. Two important trends in the data are the decrease in plasma emission measure with age on the main sequence and decreasing rotational velocity. Variability and atmospheric inhomogeneity are commonly seen, and there is considerable evidence that magnetic fields define the geometry and control the energy balance in the outer atmospheric layers. In addition, the microwave observations imply that non-thermal electrons are confined in coronal magnetic flux tubes in at least the cool dwarfs and RS CVn systems. The chromospheres in the K and M giants and supergiants are geometrically extended, as are the coronae in the RS CVn systems and probably also in other stars.

• Research Organization: National Bureau of Standards, Boulder, CO (USA)
• OSTI ID: 6932190
• Report Number(s): N-86-32377; NASA-CR-176863; NAS-1.26:176863
• Country of Publication: United States
• Language: English

Related Subjects

640102* -- Astrophysics & Cosmology-- Stars & Quasi-Stellar
Radio & X-Ray Sources
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ATMOSPHERES
DOCUMENT TYPES
DWARF STARS
ENERGY BALANCE
GIANT STARS
HEATING
MAGNETIC FIELDS
MAGNETIC FLUX
REVIEWS
STARS
STELLAR ATMOSPHERES
STELLAR RADIATION
SUPERGIANT STARS