LAUSR

Abstract We present simultaneous magnetic field measurements for the limb solar flare of 1981 July 17 using of the Ca II K, Hδ, He I 4471.5 A and Hβ lines. For two moments during the flare, which differ in time by 16 min, we analyzed Stokes I ± V profiles of these lines from observations made on the Echelle spectrograph of the horizontal solar telescope of the Astronomical Observatory of Taras Shevchenko National University of Kiev. At the time step that was close to the peak phase of the flare, all the spectral lines under study showed very wide emissions, with a full width at half maximum (FWHM) of 3.5–4 A. An interesting feature was observed in the blue wings of these lines, namely, narrow emission peaks with a FWHM of only 0.25–0.35 A. For heights of 10–18 Mm above the level of the photosphere, we found that (a) very strong kG magnetic fields (up to about 3 kG) existed at both moments of the flare, (b) the locations with strongest fields, in general, do not coincide for different spectral lines, (c) the polarities of the magnetic field for different spectral lines are in most cases identical, but sometimes they do not coincide. The data obtained indicate a significant inhomogeneity of the magnetic field in the flaring corona and the probable presence of the conditions necessary for magnetic reconnection of field lines.