Double Layers and Ion Phase-Space Holes in the Auroral Upward-Current Region

Abstract

The dynamic evolution of the boundary between the ionosphere and auroral cavity is studied using 1D and 2D kinetic Vlasov simulations. The initial distributions of three singly ionized species (H+, O+, e-) are determined from space-based observations on both sides of an inferred strong double layer. The kinetic simulations reproduce features of parallel electric fields, electron distributions, ion distributions, and wave turbulence seen in satellite observations in the auroral upward-current region and, for the first time, demonstrate that auroral acceleration can be driven by a parallel electric field supported, in part, by a quasistable, strong double layer. In addition, the simulations verify that the streaming interaction between accelerated O+ and H+ populations continuously replenished by the double layer provides the free energy for the persistent formation of ion phase-space holes.