Turbulence in flare loop and electron acceleration in solar flares
Tomoko Kawate
Queen’s University Belfast
Satoshi Masuda (Nagoya University), Shinsuke Imada (Nagoya University)
Microwave and hard X-ray emissions in solar flares have different radiation mechanisms, and differences of the radiations among flares infer characteristics of accelerated electrons. Hence, these data of nonthermal emission are powerful means for the diagnosis of accelerated particles. Another clue for examining acceleration mechanisms is in nonthermal line broadening of high temperature coronal lines. Kawate & Imada (2013) discussed that characteristics of nonthermal emissions are related to looptop turbulence that disturb electron pitch angle distribution. Therefore, simultaneous analysis of microwave, hard X-ray, and EUV/SXR line spectroscopy may tell us some valuable information on the condition of electron acceleration.
We did statistical study on the relationship between nonthermal emissions and nonthermal line broadening in solar flares with hard X-ray, soft X-ray, and microwave by using Yohkoh/HXT, Yohkoh/BCS, and Nobeyama Radioheliograph, respectively, and imagers for thermal emissions in flare loops with Yohkoh/SXT and SoHO/EIT. Comparing the timing of the peaks of their fluxes and nonthermal line width, we found that flares with rapid evaporation tend to have an earlier peak of microwave than hard X-ray, and nonthermal line broadening reaches its peak almost at the same time of the peak of nonthermal flux. On the other hand, flares with gentle evaporation tend to have peaks of microwave and hard X-ray almost simultaneously, and line broadening reaches the peak earlier. There are also some tendencies in parameters related to acceleration efficiency such as power law indices, and they suggest that turbulence in the flare loop affect the acceleration mechanism and/or its efficiency.