Dynamics of Microwave Brightness Distribution in the Giant 24 August 2002 Flare Loop

V.E. Reznikova¹, S.P. Gobikov¹, N.P. Pyatakov¹, K. Shibasaki², I.N. Myagkova³

¹Radiophysical Research Institute (NIRFI), Nizhny Novgorod, Russia
²Nobeyama Radio Observatory, NAOJ, Nagano, Japan
³Lomonosov Moscow State University, Skobeltsyn Institute of Nuclear Physics, Moscow, Russia

High resolution (5′′) radio observation of Nobeyama Radioheliograph at 34 GHz allowed to study dynamics of microwave brightness distribution along a giant flaring loop in the event 24 August 2002. The similar tendency of dynamics was found for all major temporal sub-peaks with re-distribution of the radio brightness from the footpoints (on the rising phase of each peak) to the upper part of the loop (on the decay phase). Observed dynamics is interpreted by a re-distribution of accelerated electrons number density with its relative enhancement in the looptop. Model simulations by solving the Fokker-Planck equation show that the observed dynamics is possible to obtain if the acceleration takes place near a footpoint with any pitch-angle distribution of injected electrons or in the looptop, but in the latter case the injection should occur preferably along the loop axes (“beam-like” injection).