Magnetically Induced Current Piston for Generating Extreme-Ultraviolet Fronts in the Solar Corona*

EUV waves are single-pulse, globally-propagating coronal fronts first observed in 1995 and their physical mechanism has been a subject for debate for two decades. Two distinct types of theories have been used to describe EUV waves, depending on the presumed driving mechanism: wave or pseudo-wave. We propose a hybrid model where EUV waves are compressional fronts driven by a reverse electric current layer induced from the coronal mass ejections (CMEs). The CMEs are considered as erupting flux ropes that induce the layer of electrical current. The reverse electric current layer, flowing in the opposite direction with respect to the current in the driving CME, is an eddy current layer that is necessary to maintain magnetic flux conservation in the coronal regions above the layer. The opposing CME and reverse currents mutually repel via magnetic forces with the result that the moving induced reverse current layer acts as a piston that drives a compressional perturbation in the coronal regions above the layer. This model is supported and motivated by results from 3D ideal magnetohydrodynamics (MHD) simulations and from laboratory experiments.