Dynamics of plasma vortices: The role of the electron skin depth

The drift-Alfvén equations for a quasineutral plasma that is permeated by a strong background magnetic field describe the plasma dynamics in the transverse plane. Three scalar fields—which are linear combinations of parallel current, fluid vorticity, and density—are incompressibly advected by three streaming potentials. These three "generalized vorticities" are point-wise conserved. Their dynamics is studied numerically using the method of Contour Dynamics, which for this purpose is generalized from one to three different types of vorticity. In the regime where the electron inertial skin depth de is smaller than the ion sound gyroradius, the interaction dynamics of patches of generalized vorticity shows a preference for the formation of structures with length scale O(de). In this regime quasiperiodic splitting-merging cycles of single vorticity patches occur. These vortex interactions are considered to be the paradigm for the interactions of separated vortical structures in a strongly magnetized turbulent plasm