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K.K Reeves, H.P. Warren (Harvard-Smithsonian Center for Astrophysics)
The Transition Region and Coronal Explorer (TRACE) provides some of the highest spatial resolution images ever taken of hot solar flare plasma. The TRACE 195 Å\ channel is particularly sensitive to flare plasma because of the presence of the Fe XXIV 192 Å\ resonance line in this bandpass. Using TRACE filter ratios to derive temperatures and emission measures during flares is often difficult, however, because the 171 Å\ channel is predominately hydrogen continuum emission. This emission is generally weak and often hard to distinguish from the background corona. A very large flare, such as the X2 flare observed on March 24, 2000, yields high counts in the 171 Å\ channel so that background emission becomes insignificant. Analysis of these data show steep temperature gradients below the brightest flare plasma in the arcade. These data also show large 195Å\/171Å\ ratios above the arcade, suggesting localized regions of super-hot plasma. Interpretation of the filter ratios depends on the absolute abundance of Fe, however, and we re-examine past measurements of Fe abundances in flares.
The author(s) of this abstract have provided an email address for comments about the abstract: kreeves@cfa.harvard.edu