Lower photosphere in solar active regions prior to flares and without flares. II. Physical conditions.
Abstract
Physical conditions are analyzed for the lower and middle solar photosphere in active regions prior to flares and without them. The temperature, gas pressure, and turbulent velocity are determined by comparing the observed and theoretical profiles of several Fraunhofer lines insensitive to magnetic fields. The parameters obtained for the deeper layers in flocculi without flares are in good agreement with the facula model VAL-F. The physical conditions in the lower photosphere (m ≥ 2) are found to differ for two types of active regions, the distinction becoming evident even 10 h before flares: the lines before flares are formed in denser (by 5 - 20%) and hotter (by 100 - 150K) layers, the turbulent velocity grows up to 6 - 7 km/s. In the interval from 3 - 4 h to 1 h the temperature and density excesses decrease with time. Sharp changes in all medium characteristics are observed immediately before flares - the temperature excess may reach 300K, and pressure may grow by 25%. All the distinctions diminish with growing height (in the middle photospheric layers).
- Publication:
-
Kinematics and Physics of Celestial Bodies
- Pub Date:
- 1993
- Bibcode:
- 1993KPCB....9b..50A