Modelling the topside plasma scale height based on CHAMP measurements: first results

Kurzfassung

The knowledge of the electron density distribution in the Earth’s topside ionosphere and plasmasphere is important for estimation and correction of propagation delays in GNSS, ion composition, space-weather effects on telecommunications, and other studies. Traditional ground-based ionosonde measurements cannot deliver much information about the topside electron density distribution. The CHAMP satellite, flying at a height of about 450 km, provides excellent opportunities to observe and deliver such valuable information on the topside ionosphere on a global scale. Using the GPS TEC measurements onboard CHAMP has proved to be very useful for reconstruction of the two- and three- dimensional electron density distribution. In addition, the Planar Langmuir Probe provides in-situ plasma density measurements. The purpose of this report is to present the first results in retrieving and modelling the topside plasma scale height with the help of CHAMP. The value of the scale height immediately above the F2 peak height is of crucial importance for the density reconstruction and GPS TEC calculation. The scale height is extracted from the electron profiles obtained from IRO measurements. Based on the accumulated data set, latitudinal and seasonal variations of the scale height have been already obtained for both day-time and night-time conditions. With a constantly growing CHAMP measurement data base, it will be possible to develop a new (semi-) empirical model of the plasma scale height. The model will be used to improve the model-assisted retrieval of the electron density profile by delivering an improved initial guess.