EFFECT OF THE LARGE-SCALE CONVECTION ELECTRIC-FIELD STRUCTURE ON THE FORMATION OF THIN IONIZATION LAYERS AT HIGH-LATITUDES

A three-dimensional simulation of the high-latitude ionosphere was applied to investigate the geographical distribution of E-region thin ionization layers which may be formed by the action of the convection electric field. The simulation model computes the ion densities (O+, O-2(+), N+, N-2(+), NO+, Fe+), and temperatures as a function of altitude, latitude, and longitude. The stationary state momentum and continuity equations are solved for each ion species, then the energy equation is solved for electrons, neutrals, and a generic ion having the mean ion mass and velocity. The various electric field patterns of the HEPPNER and MAYNARD [(1987) J. geophys. Res. 92, 4467-4489] convection electric field model were applied and the ionization density pattern was examined after a time sufficient for the formation of thin layers (approximate to 2000 s). It was found that large areas of thin ionization layers were formed for each of the electric field patterns examined. Southward IMF B-z conditions resulted in thin layers forming in the pre-midnight sector in the latitude range north of about 70 degrees to about 80 degrees, and after midnight between 60 and 70 degrees. For northward B-z conditions, the layers were mainly in the pre-midnight sector and covered a latitude range from about 60 to 80 degrees.