Validation of plasmasphere electron density reconstructions derived from data on board CHAMP by IMAGE/RPI data

Abstract

Plasmaspheric electron content is, beyond the ionosphere as major source, a significant contributor to the overall TEC budget affecting GNSS signals. The plasmasphere can induce half or more of the GNSS range errors caused by atmospheric electrical charges, in particular at nighttime. At DLR Neustrelitz, Germany, GPS measurements recorded onboard the LEO satellite CHAMP were used to reconstruct the topside electron density distribution (ionosphere and plasmasphere) up to GPS altitude, applying a model-based assimilation technique. In this paper, the potential of these CHAMP topside reconstructions for analyzing space weather related changes in the geo-plasma is investigated. For this purpose, comparisons are made between the CHAMP reconstructed profiles and electron densities derived from passive radio wave observations by the IMAGE RPI instrument for years 2001 till 2005.The comparison results indicate that an improvement, compared to the electron density of a background model, can be achieved by CHAMP data assimilation. The improvement is especially visible in the L-shell region below 3, which contributes notably to the GNSS signal delays. However, for the region around the plasmapause, systematical electron density underestimations of the background model w.r.t. the IMAGE data are detected. The rather limited CHAMP data coverage and the degraded observation geometry at these high altitudes seem to be not sufficient for complete compensation of this underestimation during the assimilation procedure.The results presented in this paper demonstrate the strengths of LEO TEC data assimilation, but at the same time illustrate the necessity to improve the modeling of the plasmasphere region above 4 ER L-shell distances. Furthermore, they reveal the need of additional data to establish an appropriate data base for the modeling of the complete plasmasphere.

A new electron density model of the plasmasphere for operational applications and services

“…It should be mentioned that the electron density distribution shown in Figure 12 is very similar to those derived from IMAGE satellite data published by Huang et al (2004) thus confirming our results. This finding agrees very well with the results of a comparative study of CHAMP based TIP electron density reconstructions with IMAGE data by Gerzen et al (2015). It was shown that both data sources are similar at L shells less than 3.…”

“…with topside data from IRI-2007 and other models . A previous validation of these GNSS derived plasmasphere data from CHAMP with plasmasphere density profile data from the IMAGE/RPI measurements have shown a good agreement up to about L = 3 (Gerzen et al, 2015).…”

“…To extract plasmasphere information from TIP reconstructions based on CHAMP data we assume a lower limit of altitude L min = 1.5 to avoid overlapping in the lower plasmasphere with ionosphere controlled densities. The upper limit is formally given by L ≈ 3 according to the results of a comparative study of CHAMP topside reconstructions with IMAGE data (Gerzen et al, 2015). Thus, for the high altitude part model coefficients are derived from CHAMP data obtained in the range 1.5 L 3.…”

How can GOCE and TerraSAR-X contribute to the topside ionosphere and plasmasphere research?

“…[] have developed an assimilation technique for reconstruction of the ionosphere/plasmasphere structures using for GPS POD measurements onboard CHAMP (CHAllenging Minisatellite Payload) satellite (altitude ~400 km). This approach was further implemented in DLR (German Aerospace Center) for CHAMP 2‐D reconstruction of the topside ionosphere and plasmasphere [ Jakowski et al ., ; Gerzen et al ., ]. Yizengaw et al .…”

Consistency of seven different GNSS global ionospheric mapping techniques during one solar cycle

“…The new 3D model development is actually in the coding and testing stage. In addition, this new 3D approach will be augmented by a new model for the plasmasphere/plasmapause currently developed in a cooperation project with Deutsches Zentrum fr Luft-und Raumfahrt (DLR) Neustrelitz (more details can be found in [8] and [9]). The current single layer model processing and software will only retained as long as the new 3D model is not yet operational.…”