Source Structures of the 1998 November 28 X-Class Flare and Electron Acceleration

We studied the 1998 November 28 X-class flare, which showed long-duration, two-ribbon Hα emission. (1) A soft X-ray loop system developed along the major magnetic neutral line in the impulsive phase. Hard X-ray and microwave emissions due to nonthermal electrons were located in some limited regions. While the compact hard X-ray loop was associated with weak, diffuse soft X-ray emission, two large microwave loops did not have soft X-ray counterparts. (2) Time profiles of two large microwave loops were similar to that of hard X-ray total emission, which emanated mostly from the compact source, even in the fine time structure in the rising phase. (3) A super-hot thermal hard X-ray source appeared around the impulsive peak and was located along the major magnetic neutral line in the declining phase, coinciding with the bright soft X-ray emission. The thermal component can be explained within the standard reconnection model to the extent that the super-hot thermal plasma was heated in the large soft X-ray loop. However, the nonthermal electrons were accelerated in a localized region where three loops interacted with each other. The inferred configuration may be a more complicated form of the double-loop interaction model proposed by Hanaoka (1996) and Nishio et al. (1997).