Magnetic field strucrure in weak solar flares on photospheric and chromospheric levels

Abstract

The spectrophotometric measurement's results of four weak solar flares of 25 July 1991, 18 July 2000, 9 June 2001 and 28 July 2004 are presented. The importances of these flares were SB, C1.5, C4 and C4 respectively. The Stokes I±V profiles of Нα, D_1 NaI and other metalic spectral lines (mainly FeI) were analyzed. It was found that magnetic field in just one flare was stronger on the chromospheric level than in the photosphere according to a uniform magnetic field approximation. The splitting's characteristics of I±V Stokes profiles in chromospheric lines pointed out dual picture: quasihomogeneous field in a horizontal plane and inhomogeneous, at least were both two-component. The parameters of two-component magnetic field's model were calculated for flare of 25 July 1991. As a result, it was shown that magnetic field of small-scale component was 10–20 times stronger than magnetic field of background component and lines profiles were 5 times narrower than observed ones.

Keywords

• structure of solar magnetic fields
• solar flares