Observation of Ionospheric Effects in the Aurora Zone using CHAMP and COSMIC/Formosat-3 Data

Mayer, C. and Jakowski, N.

German Aerospace Center/ Institute of Communication and Navigation, Neustrelitz, Germany

We present observations of the auroral ionosphere combining radio occultation data from the CHAMP and from the COSMIC/Formosat-3 satellite missions. The CHAMP radio occultation measurements with about 150 vertical electron density profiles per day enables us to study solar-cycle dependencies since the beginning of observations in April 2001. With more than 2500 profiles per day the COSMIC/Formosat-3 offers an unprecedented temporal and spatial data coverage since April 2006.

The developed algorithms for analyzing the shape of the vertical electron density profiles up to 800km height fit an empirical Ansatz to the data. This approach consists of Chapman functions for the E- and F-layers and of an exponential decay for the topside. Using this technique, we select profiles with pronounced ionization at E-Layer height in the range of about 90-150 km for studying the geophysical conditions and characteristics of the related ionospheric processes.

In particular we show that profiles with enhanced E-layer ionization are closely related to the location and shape of the auroral zone. Thus, we are able to study the local-time, seasonal, and space-weather dependence of enhanced ionization prozesses in the auroral zone, e.g. related electron precipitation processes of magnetospheric origin. Furthermore, we present a statistical analysis of the F-layer parameters and the plasmasphere scale height at 600-800 km height for both auroral zones.