Characterization of topside ionospheric scale height based on COSMIC occultation observations

The topside ionosphere is the region of the ionosphere above the altitude where the F₂ layer electron density maximum is located. Occultation observations can provide the entire ionospheric electron density profile from the ground to the orbital altitude of LEO satellites, which is important for the study of the topside ionosphere. The topside scale height is an important parameter for the construction of the ionospheric electron density profile model above the top. In this paper, we extract the top scale height of the effective electron density profile data using the constellation observing system for meteorology, ionosphere and climate (COSMIC) occultation observations from 2007 to 2020, analyze its characteristics with local time, season, latitude, longitude, and solar activity level. The results show that: the topside scale height has obvious daily and seasonal variation patterns and shows strong dependence on solar activity; the latitudinal variation of the topside scale height is strongly dependent on the local time and shows a distinct wave structure in the east-west longitude direction, which has different morphologies in the northern and southern hemispheres; the topside scale height has a significant east-west longitudinal difference in the summer hemisphere, more pronounced in the southern hemisphere in summer.