Relaxation of 2D turbulence to a metaequilibrium near the minimum enstrophy state

Abstract

Relaxation of 2D turbulence has been measured in magnetized electron columns, which follow the same (r,\ensuremath{\theta}) dynamics as 2D incompressible fluids. The turbulence arises from shear instabilities on initially hollow columns, then relaxes to long-lasting, axisymmetric metaequilibria. The measured metaequilibrium vorticity profiles are in close agreement with the minimum enstrophy vortices predicted by the ``selective decay'' hypothesis.