The Evolution of Solar Active Regions Based on 8.6 mm and Other Solar Observations.
Abstract
Extreme ultraviolet (EUV) and radio (8.6mm) observations have been analyzed in order to obtain information about the chromospheric layers of solar quiet and active regions. Correlations between EUV lines, EUV continua and 8.6 mm radiation have been obtained. On the basis of these correlations and theoretical considerations the authors suggest that as a first approximation EUV chromospheric lines are formed at the same temperatures in quiet and active regions. The increased density in active regions causes an increase in EUV chromospheric emission through a reduction in the non-LTE departure coefficients. The 8 mm brightness temperature increases in active regions because the larger optical depth causes the 8 mm radiation to be emitted from higher and hotter layers in active regions than in quiet regions. The authors also find, as expected, a good correlation between the flaring rate of active regions and their 8 mm brightness temperatures. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 1973
- Accession Number
- AD0774021
Entities
People
- George L. Withbroe
- Jorge E. Vernazza
Organizations
- Harvard College Observatory