Modelling of the ionosphere and plasmasphere with SWARM

Kurzfassung

Plasmaspheric electron content is, beyond the ionosphere as major source, a significant contributor to the overall TEC budget affecting GNSS signals. So the plasmasphere can contribute up to half or even more of the GNSS range errors. GNSS measurements onboard SWARM and in-situ data of the SWARM mission together with ionospheric measurements, available onboard of the LEO-satellites GRACE, TerraSAR- and Tandem-X, offer a unique opportunity for more comprehensive multi-sensor data driven modelling of the global 3D topside ionosphere and plasmasphere. Especially the specific SWARM satellite constellation facilitates a deeper analysis of the space weather related changes and disturbances in the geo-plasma and a detailed studying of solar-terrestrial relationship during severe space weather events. Most notable in the regions with sparse ground-based GNSS data coverage, the contribution of the LEO GNSS and ionospheric radio occultation data for monitoring the ionospheric impact on transionospheric radio systems is of particular interest. At German Aerospace Center (DLR) GPS measurements recorded onboard the LEO-satellite CHAMP (cf. Reigber et al., 2000) were used to reconstruct the topside ionosphere and plasmasphere electron density distribution in the vicinity of the CHAMP orbit plane (cf. Fig. 1). In this presentation we show results of the comparisons made between the CHAMP reconstructions and the in situ electron densities derived from passive radio wave observations by the IMAGE RPI instrument (Reinisch et al., 2001) for years 2001 till 2005. Our investigations indicate an improvement achieved by CHAMP data assimilation, especially visible in the L-shell region below 3 Earth’s Radii. However, for the region around the plasmapause, the rather limited CHAMP data coverage and the degraded observation geometry seem to be not sufficient for complete compensation the background model caused underestimation. We expect that SWARM data, in particular by utilizing the formation flight capabilities of the SWARM mission, will considerably improve the situation.