TRACE and RHESSI observations of white-light flares

TRACE gives a photometrically stable, high-resolution view of the visible and UV emissions of solar flares, with enough diagnostic power to distinguish photospheric from chromospheric contributions. These emissions dominate the radiant energy of a flare and correspond well with hard X-ray emission in the impulsive phase. We survey these data with reference to well-observed events of 4~October~2002 and 4~November~2003, on the disk (M4; S19W09) and on the limb (X17; S19W83) respectively. We analyze the spatial and temporal properties of the footpoint sources in these two events, characterizing their physical parameters (contrast, image gradients, apparent motions). The brightest kernels of the 4~October~2002 event have intensities twice that of the quiet photosphere, and have sizes close to the Nyquist limit of the TRACE pixels (0.5~arc~sec). The white-light footpoint sources can be considered as a proxy for the target region of fast electrons studied via hard X-ray bremsstrahlung. We compare RHESSI hard X-ray footpoint sources with their white-light counterparts and estimate filling factors for the hard X-ray emission itself.