ABSTRACT
In Figure 4.5 we display the evolution of two blocks of vorticity (one positive, one negative) in two-space dimensions, evolving under the influence of a con stant negative magnetic field uh = —1, with no flux pinning and no boundary nucleation of vorticity. As in the equivalent one-dimensional figure, Figure 4.1, we see that as time evolves some of the positive and negative vorticity cancel each other out. However in this case a block of negative vorticity remains in the steady state. Figure 4.6 displays the same results as Figure 4.5, with contour plots of the vorticity Wh• The steady-state problem in this situation can be formulated as an obstacle problem [12].
