Space weather monitoring by GPS measurements on board CHAMP

Abstract

The availability of L-band radio signals permanently transmitted by satellites of the Global Positioning System (GPS) has opened a new dimension for ionosphere sounding. Whereas ground-based GPS measurement techniques have been developed already over many years, the space-based GPS measurements on board Low Earth Orbiting (LEO) satellites are rather new. GPS measurements onboard the German georesearch satellite CHAMP were used to monitor the ionosphere on global scale since April 2001. Addressed here are the capabilities of the ionospheric radio occultation (IRO) technique for routinely monitoring the global ionosphere with the purpose of deriving value-added data products and studying ionospheric perturbations. Also discussed is the use of zenith viewing GPS navigation data for reconstructing the three-dimensional electron density distribution of the topside ionosphere/plasmasphere in the vicinity of the CHAMP orbit plane. Whereas the ground-based measurements show strong horizontal redistribution of plasma during ionospheric storms, the space-borne measurements indicate a severe vertical redistribution of the ionospheric plasma during the selected events. In this paper we review the capabilities of the space-based GPS measurements performed on board CHAMP and discuss ionospheric/plasmaspheric perturbation processes caused by the strong space weather event on 20 November 2003. Space-based GPS measurements have a high potential for routinely monitoring the ionosphere/plasmasphere systems, thus effectively contributing to global space weather monitoring activities. Copyright 2007 by the American Geophysical Union.