COORDINATED OPTICAL AND YOHKOH OBSERVATIONS OF 26 JUNE 1992 FLARE LOOPS

Optical spectra of large flare loops were detected by the Ondrejov Mul tichannel Flare Spectrograph (MFS) during coordinated observations wit h MSDP at Pic du Midi (Halpha) and the soft X-ray telescope (SXT) on Y ohkoh. The CCD video images taken by the MSF slit-jaw camera document the time-development of the flare loops as seen through the Halpha fil ter. Preliminary analysis of the MSDP images shows the intensity struc ture of the cool flare loops and their velocity fields. From the spect ra we can clearly see the intensity variations along the cool loops. S XT images show the structure of hot X-ray loops similar to that of coo l loops. Special attention is devoted to the bright tops, simultaneous ly observed in X-rays, Halpha and other optical lines. Based on a prel iminary analysis of the optical spectra, we speculate about possible m echanisms leading to an observed bright emission at the tops of cool l oops. We suggest that direct soft X-ray irradiation of cool loops at t heir tops could be, at least partly, responsible for such a strong bri ghtening.