Nonlinear Evolution of Plasma Enhancements in the Auroral Ionosphere I: Long Wavelength Irregularities

摘要

The linear stability and nonlinear evolution of plasma enhancements in arbitrary ambient electric fields in the diffuse auroral F region ionosphere have been studied using analytical and numerical simulation techniques. Our results that equatorward convecting plasma slabs initially limited in latitudinal extent are primarily destabilized on their poleward sides by a combination of the effects of convection and field aligned currents. Furthermore we find that the plasma enhancements break up into primary striation-like structures (elongated in the north-south direction for equatorward convection) which can form and cascade from large (approx. = 100 km) to smaller (approx. = 3 km) scale sizes on the order of an hour. The primary and associated smaller scale structures can be oriented either in the north-south or east-west (L-shell alignment) direction depending on the ambient electric field magnitude and direction.