HR: 1330h
AN: SM12A-1210    [PDF]
TI: Small-Scale, Field-Aligned Currents at the Top-Side Ionosphere
AU: * Christiansen, F
EM: fch@dmi.dk
AF: Danish Meteorological Institute, Lyngbyvej 100, Copenhagen, DK-2100 Denmark
AU: Neubert, T
EM: neubert@dsri.dk
AF: Danish Space Research Institute, Juliane Maries Vej 30, Copenhagen, DK-2100 Denmark
AB: High-precision vector magnetic field observations from the {\O}rsted satellite are used to investigate small-scale, field-aligned currents on spatial scales down to 600 m. Placed in a low-Earth, polar orbit, the slowly drifting orbit plane has covered all local times since launch in 1999 with more than 25000 polar passes. Small-scale currents are primarily found in the cusp with densities of 10-100 $\mu$Am$^{-2}$, reaching more than 1000 $\mu$Am$^{-2}$ during disturbed conditions. These values are 1-2 orders of magnitude larger than large-scale region 1 and 2 currents. Current densities are 2-4 times larger when the ionosphere is illuminated than when in darkness. While the location of currents follows the changes in cusp location with changing IMF, the intensity of the currents seems to depend on the level of solar wind turbulence. The data suggest that small-scale currents may be associated with significant local heating of the ionosphere and thermosphere.
DE: 2409 Current systems (2708)
DE: 2475 Polar cap ionosphere
DE: 2708 Current systems (2409)
SC: SPA - Magnetospheric Physics [SM]
MN: 2003 Fall Meeting