Detection of acceleration processes during the initial phase of the 12   June 2010 flare
  We present an analysis of the plasma parameters during the initial phase of the 12 June 2010 flare (SOL2010-06-12T00:57). A peculiarity of the flare was the detection of $\gamma$--emission that is unusual for such weak and short event. The analysis revealed the presence of a flare precursor detected about 5 minutes before the flare onset in 94 \AA \ images which spatially coincided with the non-polarized microwave (MW) source at 17 GHz (\textit{the Nobeyama Radio Heliograph}) that is the Neutral Line associated Source (NLS). A comparison of the results obtained from MW data by \textit{the Nobeyama Radio Polarimeters} and \textit{the multi-frequency Siberian radioheliograph} (the new 10-antenna radio heliograph prototype at 4.6 and 6.4 GHz) and hard X-ray (HXR) observations by \textit{the Fermi Gamma-ray Space Telescope} reveal the presence of accelerated electrons during the flare initial phase. The analysis of MW and HXR spectra also confirms the presence of accelerated particles. Moreover a good temporal correlation between several lightcurves in different HXR energy bands and at MW frequencies indicates generation of both HXR and MW emission by a common population of accelerated electrons. Detection of accelerated particles during the initial phase of the flare and soft-hard-harder (SHH) behavior of the spectra indicate several episodes of particle acceleration and confirm the non-impulsive type of the flare evolution. 
L.K. Kashapova, N.S. Meshalkina, M.S. Kisil
astro-ph.SR