COMPREHENSIVE MULTIWAVELENGTH OBSERVATIONS OF THE 1992 JANUARY 7 SOLAR-FLARE

Observations of a solar flare that occurred at 2022 UT on 1992 January 7, during the 1991 December/ 1992 January Max '91 campaign, are prese nted. This flare was observed simultaneously in H alpha, radio (at mic rowave and millimeter wavelengths), and soft and hard X-rays (by the Y ohkoh spacecraft) with high spatial and moderate spectral resolution. A comparison of magnetograms before and after the flare shows evidence of the emergence of new magnetic flux of opposite polarity at the fla re site. Although this flare was only of moderate size (GOES classific ation C8.9 and H alpha importance SF), it exhibited several distinct b ursts and at least 10 spatially distinct hard/soft X-ray sources. Cosp atial H alpha brightenings suggest that most of the X-ray sources are located at footpoints of magnetic loops. Two of the hard X-ray sources have no H alpha counterparts and are therefore believed to be located at loop tops. The flare consisted of three bursts of particle acceler ation followed by a purely thermal phase. High spectral resolution Ca XIX line profiles indicate upflows shortly after the second accelerati on phase. Analysis of the microwave/hard X-ray/soft X-ray emission fro m individual sources provides information on the radio emission mechan isms, the energetic electron population, the magnetic held strength, a nd the plasma density. These parameters were estimated for the two mic rowave sources observed during the third acceleration burst; these sou rces were simultaneously detected in soft X-rays, and one of the sourc es is also seen in hard X-ray maps. Although the microwave emission is consistent with the gyrosynchrotron mechanism, the millimeter emissio n, which peaks during the thermal phase when all nonthermal activity h as ceased, is likely due to thermal bremsstrahlung from the soft X-ray -emitting hot plasma. The energy lost to collisions by the energetic ( >15 keV) electrons and the energy contained in the thermal plasma are calculated for each source. The energy injected by the nonthermal elec trons from all sources is estimated to be similar to 10(30) ergs. Only the soft X-ray sources with gradual time profiles seem to show the Ne upert effect.