Strong magnetic fields in solar flares: observational data and a theoretical model.
Abstract
Spectral observations of five solar flares made in 1981 and 1989 with a circular-polarization analyzer at the echelle spectrograph of the horizontal solar telescope of the Kiev University Astronomical Observatory are analyzed. Direct measurements of the Zeeman splitting of the emission of Fe I, Fe II, Na I, He I and H I lines indicated that the intensity of the longitudinal magnetic field H ∥ in the flares ranges from 10 - 20 to 350 mT, and that He∥ = 120 - 180 mT at the points at which He I emission is formed. The field HP∥ at photospheric level, measured in the splitting of the Fraunhofer profiles, is systematically lower than the emission He∥. This may indicate the existence of a local (vertically) intensification of the magnetic field in flares. It is shown that a theoretical model according to which strong fields arise as a result of twisting of magnetic flux tubes in the upper levels of the solar atmosphere agrees satisfactorily with the observational data.
- Publication:
-
Kinematics and Physics of Celestial Bodies
- Pub Date:
- 1991
- Bibcode:
- 1991KPCB....7f..25L