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Prominence Activation by Coronal Fast Mode Shock
An X5.4 class flare occurred in active region (AR) NOAA11429 on 2012 March 7.
The flare was associated with very fast coronal mass ejection (CME) with its
velocity of over 2500 km/s. In the images taken with STEREO-B/COR1, a dome-like
disturbance was seen to detach from expanding CME bubble and propagated
further. A Type-II radio burst was also observed at the same time. On the other
hand, in EUV images obtained by SDO/AIA, expanding dome-like structure and its
foot print propagating to the north were observed. The foot print propagated
with its average speed of about 670 km/s and hit a prominence located at the
north pole and activated it. While the activation, the prominence was strongly
brightened. On the basis of some observational evidence, we concluded that the
foot print in AIA images and the ones in COR1 images are the same, that is MHD
fast mode shock front. With the help of a linear theory, the fast mode mach
number of the coronal shock is estimated to be between 1.11 and 1.29 using the
initial velocity of the activated prominence. Also, the plasma compression
ratio of the shock is enhanced to be between 1.18 and 2.11 in the prominence
material, which we consider to be the reason of the strong brightening of the
activated prominence. The applicability of linear theory to the shock problem
is tested with nonlinear MHD simulation
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