The ongoing research carried out by the solar community has been reported in the proceedings of several recent symposia, seminars and workshops, as well as in scientific journals (Kane et al. 1983, Švestka et al. 1982a, Shea et al. 1984, Kundu S Woodgate 1984, Simon 1984). We summarize here some of the novel results with reference to flare research as far as SMM data analysis is concerned. Understanding of impulsive phase phenomena was one of the primary goals of the SMM. The early reports from the analysis of the first ever obtained high-resolution images in the <30 keV energy range stressed the fact that some flares showed hard x-ray (HXR) bright sources at the feet of coronal loops (Hoyng et al. 1981a, b, Machado et al. 1982, Duijveman et al. 1982), the so-called HXR “footpoints,” favoring the thick-target beam mechanism for the production of HXRs, and indicating acceleration efficiencies >20% during the early impulsive phase. This phenomenon was shown to be accompanied by soft x-ray (SXR) line broadening, indicative of strong turbulence, and the immediate appearance of blue shifted spectral lines, which shows that plasma heated to >10-1 K rises from the footpoints of loops with velocities to 300 km s-1 (Antonucci et al. 1982, Antonucci et al. 1984a). This result provides a strong indication of the chromospheric evaporation phenomenon, which has been confirmed in analyses of combined SXR and Ha observations (Acton et al. 1982, Gunkler et al. 1984).
Explosive Chromospheric Evaporation Driven by Nonthermal Electrons around One Footpoint of a Solar Flare Loop