Ionospheric Signatures of Plasmaspheric Plumes over Different Longitudinal Sectors: A Comprehensive Study

Twenty-six different plasmaspheric plumes were identified during 2001 from the IMAGE EUV database. Simultaneously the two-dimensional structure of global GPS TEC (total electron content) data has been imaged using several sources: JPL's interpolated Global Ionosphere Maps (GIM) and MIT's Madrigal GPS TEC data. IONEX 2-hour averaged TEC maps were also examined, but they were not helpful in verifying the transient plumes' signatures. Both model and measurement data have observed plumes of greatly elevated GPS TEC, which is associated with the erosion of the outer plasmasphere by strong sub-auroral polarization (SAP) electric fields, even in regions other than North America. We mapped the plasmapause and plume position, extracted from IMAGE EUV data, to the equatorial plane and compared it with GPS TEC maps. GIM data were able to show sharp changes in TEC gradient, but did not have enough resolution to agree with plumes anywhere other than above North America. Generally, we found reasonably good agreements between these independent observations; In particular the comparison with Madrigal GPS TEC was excellent at different longitudinal sectors.