VORTEX-VORTEX INTERACTION MEDIATED MOTION OF VORTICES IN JOSEPHSON-JUNCTION ARRAYS

We numerically study vortex motion in arrays of over- and under-damped Josephson junctions. We show quantitatively that vortex-vortex intera ctions (WI) in a vortex-street are large enough to overcome the pinnin g potential and cause vortices to move even in a region with no extern al current. The experiments of van der Zant et al. are reinterpreted i n terms of WI without invoking ballistic motion of vortices. The discr epancy with simulations which have all failed to observe any ballistic motion is thus removed. Our results also indicate that the vortex mas s is negligible for the McCumber-Stewart parameter, beta(c) < 100.