Topside plasma scale height retrieved from radio occultation measurements

The plasma scale height is one of the important ionospheric characteristics due to its intrinsic connection to the ionospheric plasma temperature and composition, and thus to the shape of the electron density profile. Therefore, the knowledge of the plasma scale height values and variation is of crucial importance when addressing several open scientific and technological questions such as the upper ionosphere temperature balance, ion composition, storm dynamics, etc. While the plasma scale height value in the bottomside ionosphere can be deduced directly and reliably enough by vertical incidence sounding, the plasma scale height in the topside ionosphere is difficult to obtain. The ionospheric radio occultation (IRO) technique, based on low-earth-orbiting (LEO) satellites, is capable of delivering valuable information on the topside plasma scale height behaviour and of providing a rich database for consequent development of new empirical models of the plasma scale height and density. The purpose of this paper is to present a new procedure for retrieval of the topside plasma scale height value from IRO measurements by the LEO satellite CHAMP. First results from the analysis of the topside plasma scale height’s temporal and spatial variations are also provided.