Why are there stationary EIT wave fronts

EIT waves are often observed to be propagating EUV enhancements followed by an expanding dimming region after the launch of CMEs. It was widely assumed that they are the coronal counterparts of the chromospheric Moreton waves, though the former are three or more times slower. The existence of a stationary “EIT wave” front in some events, however, posed a big challenge to the wave explanation. Simulations are performed to reproduce the stationary “EIT wave” front, which is exactly located near the footpoint of the magnetic separatrix, consistent with observations. The formation of the stationary front is explained in the framework of our model where “EIT waves” are supposed to be generated by successive opening of the field lines covering the erupting flux rope in CMEs.