Line profiles and magnetic fields in the limb solar flare of July 17, 1981. Preliminary results

Abstract

The limb solar (cid:29)are of 17 July 1981 is studied according to the observations carried out with the Echelle spectrograph of a horizontal solar telescope of the Astronomical Observatory of Taras Shevchenko National University of Kiev. For 8 h 17 m UT, close to the (cid:29)ash phase, the I ± V pro(cid:28)les of the K Ca II 3933.7 (cid:6)A and He I 4471.5 (cid:6)A lines are analyzed. At the indicated moment, these lines had two components of emission, narrow and wide, which were mutually shifted on 1.8(cid:21)2 (cid:6)A. The narrow component had a full half-width of 0.24 (cid:6)A in the K Ca II line and 0.34 (cid:6)A in the He I line. The wide component had the full half-widths of 3.3 (cid:6)A and 4.1 (cid:6)A, respectively, for these lines. The magnetic (cid:28)eld magnitude in the (cid:29)are, measured by splitting the narrow component, varies in the picture plane and reaches 1300 ± 200 G for the K Ca II line and 2100 ± 200 G for the He I line. Such features are found at the altitudes of about 10(cid:21)14 Mm above the level of the photosphere. It is important to note that the true values of the local magnetic (cid:28)elds in the (cid:29)are could be even larger, since the obtained results represent a longitudinal component of the magnetic (cid:28)eld, with the assumption that the (cid:28)lling factor equals unity. On the basis of the comparison of the Doppler widths of the narrow component in the two lines under study, the following estimations of kinetic temperature and turbulent velocity were obtained: T = 17000 ± 1000 K, and ξ turb = 10 . 8 ± 0 . 3 km/sec.