Abstract
A new method has been developed to retrieve neutral temperature T n and composition [O], [N 2 ], [O 2 ] from electron density profiles in the daytime mid-latitude F 2 -region under both quiet and disturbed conditions. A comparison with CHAMP neutral gas density observations in the vicinity of Millstone Hill Incoherent Scatter Radar (ISR) has shown that the retrieved neutral gas densities coincide with the observed ones within the announced accuracy of CHAMP observations, provided that accurate N e ( h ) ISR profiles are used for the retrieval. The performance of the method has also been tested ingesting Digisonde N e ( h ) profiles. In this case the agreement with CHAMP neutral gas density observations is less successful. Possible factors that can influence the performance accuracy are investigated. These are mostly related to limitations due to the ionogram scaling and inversion methods, including performance limitations of the sounding technique itself, like for instance during G-conditions. Several tests presented here demonstrate that discrepancies in the hmF2 values provided by the Digisondes could have an important impact on the performance of the method. It should be noted that in all tests performed here using Digisonde N e ( h ) profiles, the topside part is approximated with the NeQuick model and any assessment concerning the impact of the topside profiler on the accuracy of the method is beyond the scope of this investigation. Despite the limitations related to the use of Digisonde profiles, the proposed method has the potential to monitor the thermosphere at least with ISR N e ( h ) profiles. Digisonde electron density profiles can also be used if quality improvements are made concerning the ionogram inversion methods.
Highlights
Hundreds of communication, military, navigation satellites orbit around the Earth and those below 2000 km are subjected to drag due to collision with the atmospheric particles
A comparison with CHAMP neutral gas density observations in the vicinity of Millstone Hill Incoherent Scatter Radar (ISR) has shown that the retrieved neutral gas densities coincide with the observed ones within the announced accuracy of CHAMP observations, provided that accurate Ne(h) ISR profiles are used for the retrieval
The obtained results tell us that the proposed method seems to be efficient if reliable ISR Ne(h) profiles are used. This is an important result as a vast database with Millstone Hill ISR observations under various geophysical conditions exists and a possibility to extract basic thermospheric parameters from these observations is of great interest
Summary
Military, navigation satellites orbit around the Earth and those below 2000 km are subjected to drag due to collision with the atmospheric particles This collision slows down the spacecraft causing it to drop to lower altitudes. During the great geomagnetic storm of 13–14 March 1989, tracking of thousands of space objects was lost and it took North American Aerospace Defence Command many days to reacquire them in their new, lower, faster orbits. Another classic case was the premature loss of Sky Lab. Geomagnetic activity was so severe, for such an extended period, that Sky Lab de-orbited and burned in before a planned Space Shuttle rescue mission was ready to launch. The development of methods to monitor and forecast atmospheric drag effects on satellites is a very actual problem with strong economic consequences
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