  We report a strong association between the particle acceleration and plasma
motions found in the 2010 August 18 solar flare. The plasma motions are tracked
in the extreme-ultraviolet (EUV) images taken by the Atmospheric Imaging
Assembly (AIA) on board the Solar Dynamics Observatory and the Extreme
UltraViolet Imager (EUVI) on the Solar Terrestrial Relation Observatory
spacecraft Ahead, and the signature of particle acceleration was investigated
by using Nobeyama Radioheliograph data. In our previous paper, we reported that
in EUV images many plasma blobs appeared in the current sheet above the flare
arcade. They were ejected bidirectionally along the current sheet, and the
blobs that were ejected sunward collided with the flare arcade. Some of them
collided or merged with each other before they were ejected from the current
sheet. We discovered impulsive radio bursts associated with such plasma motions
(ejection, coalescence, and collision with the post flare loops). The radio
bursts are considered to be the gyrosynchrotron radiation by nonthermal high
energy electrons. In addition, the stereoscopic observation by AIA and EUVI
suggests that plasma blobs had a three-dimensionally elongated structure. We
consider that the plasma blobs were three-dimensional plasmoids (i.e. flux
ropes) moving in a current sheet. We believe that our observation provides
clear evidence of particle acceleration associated with the plasmoid motions.
We discuss possible acceleration mechanisms on the basis of our results.
