A scenario of the X4.8 flare of 2002 July 23 based on RHESSI and TRACE observations

From an inter-comparison among TRACE, RHESSI, and Hα images of the X4.8 flare of 2002 July 23, we found it to be a typical two-ribbon flare. The Hα and TRACE 195Å images are all shown to have the two-ribbon pattern, while the TRACE 195Å images show also a loop-arch whose footpoints deviate slightly from the ribbons. The TRACE 195Å ribbons match well the higher energy hard X-ray images. During the impulsive phase, the hard X-ray images above 38 keV present a low-lying loop connecting the two ribbons of TRACE 195Å. Above the low-lying loop, there is a coronal low energy hard X-ray source. The spatial structure and evolutionary patterns as a whole are presented. Possible theoretical explanations are briefly discussed.