THE MICROWAVE AND H-ALPHA SOURCES OF THE 1992 JANUARY 13 FLARE

We compare X-ray, microwave and Ha observations for the 1992 January 1 3 limb flare. The soft and hard X-ray images of this flare have been s tudied thoroughly by Masuda et al. (1994) with Yohkoh SXT and HXT imag es. We find that during the hard X-ray emission peak there is no Ha br ightening on the disk nor at the limb, so the main ribbons of this fla re must be beyond the limb. The microwave source maintains a fixed dis tance about 10 '' from the optical limb in the frequency range 2.8-14. 0 GHz. We interpret this limit in source position as due to the presen ce of a microwave limb that extends higher than the white-light limb-t o a height of 7300 +/- 1500 km. We believe that the high-frequency mic rowave emissions are occulted by this extended limb, while the soft an d hard X-ray emissions are able to pass through largely unaffected. We also believe, however, that the hard X-ray footpoints are also partia lly occulted by the photospheric limb, despite the appearance of ''foo tpoint sources'' in HXT data shown by Masuda et al. The smooth X-ray a nd microwave time profiles, microwave-rich emission relative to hard X -rays, and progressive hard X-ray spectral hardening through the flare peak are all characteristics that we interpret as being a direct resu lt of the occultation of footpoint emission.