HR: 11:05h
AN: SA32C-04    [Abstracts]
TI: Satellite observations of penetration electric fields during a severe magnetic storm
AU: * Lin, C S
EM: chin.lin@bc.edu
AF: Insitute for Scientific Research, Boston College, Chestnut Hill, MA 02467 United States
AU: Yeh, H
AF: Institute of Space Science, National Central University, Chung-Li, 300 Taiwan
AB: During the severe magnetic storm of July 15, 2000, the ROCSAT-1 low earth orbiting satellite detected an unusually large region of density depletion at low latitudes (<35o) in the nightside ionosphere in co-rotation with the Southern Atlantic Anomaly (SAA). Adjacent to the region of density dropout was a region of density enhancement with irregularities. We deduced convective electric fields during the storm from measurements of drift meters and retarding potential analyzer (RPA) on board ROCSAT-1. Large eastward zonal and outward radial electric fields were detected at apex height below 5000 km. The magnitude of the radial electric field was about 10 mV/m in the beginning of storm main phase and decayed to about 1-2 mV/m during the recovery phase. The zonal electric field followed the similar variation with a smaller magnitude. Electric fields were perturbed with distinct localized features in association with density depletion and enhancement structures in the SAA region. The mean magnitude of electric fields increased as density decreased in the density depletion region. The zonal and radial electric fields were generally reduced in the density enhancement region, suggesting an appreciable enhancement of ionospheric conductivities. Interestingly electric fields in the density enhancement region contained distinct wavy structures with wave length about 100 km. Both electric field components peaked at the apex height of discontinuity separating the density depletion and enhancement. These results suggest that feedback effects in the SAA region are important for the electric field penetration to the low latitude nightside ionosphere.
DE: 2411 Electric fields (2712)
SC: SPA-Aeronomy [SA]
MN: 2004 AGU Fall Meeting