A SUPERHOT FLARE OBSERVED BY YOHKOH

We report the first solar flare for which direct X-ray imaging (with f ocusing optics) has shown the location of superhot (T similar to 30 MK ) plasma. This hare consists of two separate loop structures. The smal ler structure dominates the soft X-ray emission, but the longer struct ure develops with persistently higher temperatures, which overlaps wit h low-energy hard X-ray sources with very soft spectra. Using a two-te mperature model, we describe how the soft X-ray images lead to the inf erence of superhot temperatures in the latter structure, as we combine three broadband measurements at slightly different effective waveleng ths.