Accession Number : AD0774021

Title :   The Evolution of Solar Active Regions Based on 8.6 mm and Other Solar Observations.

Descriptive Note : Final rept. 1 Jan-30 Jun 73,

Corporate Author : HARVARD COLL OBSERVATORY CAMBRIDGE MASS

Personal Author(s) : Vernazza,Jorge E. ; Withbroe,George L.

Report Date : JUL 1973

Pagination or Media Count : 34

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)

Descriptors :   *Chromosphere, *Solar radiation, Solar activity, Solar ultraviolet radiation, Millimeter waves, Correlation techniques

Subject Categories : Astrophysics

Distribution Statement : APPROVED FOR PUBLIC RELEASE