Abstract
For the first time thermospheric parameters (neutral composition, exospheric temperature and vertical plasma drift related to thermospheric winds) have been inferred for ionospheric G-conditions observed with Millstone Hill ISR on 11–13 September 2005; 13 June 2005, and 15 July 2012. The earlier developed method to extract a consistent set of thermospheric parameters from ionospheric observations has been revised to solve the problem in question. In particular CHAMP/STAR and GOCE neutral gas density observations were included into the retrieval process. It was found that G-condition days were distinguished by enhanced exospheric temperature and decreased by ~2 times of the column atomic oxygen abundance in a comparison to quiet reference days, the molecular nitrogen column abundance being practically unchanged. The inferred upward plasma drift corresponds to strong ~90 m/s equatorward thermospheric wind presumably related to strong auroral heating on G-condition days.
Highlights
Ionospheric F2 -layer is the main layer in the Earth’s ionosphere with maximum electron concentration Nm F2, which is normally larger than in other ionospheric layers under various geophysical conditions
Excellent CHAllenging Minisatellite Payload (CHAMP)/STAR and GOCE neutral gas density (ρ) observations are used in our analysis
We have revealed a strong decrease of atomic oxygen abundance, presumably related to the transfer of disturbed neutral composition from the auroral zone
Summary
Ionospheric F2 -layer is the main layer in the Earth’s ionosphere with maximum electron concentration Nm F2 , which is normally larger than in other ionospheric layers under various geophysical conditions. Sometimes F2 -layer disappears on the ground-based sounding ionograms due to its blanketing by underling F1 -layer telling us that critical frequency fo F2 becomes ≤ fo F1. According to the URSI handbook of ionogram interpretation and reduction [1], such situation is referred to as G-condition. G is just a descriptive letter indicating conditions of ground-based ionospheric sounding observations. During G-conditions no ionospheric information is available from the heights above F1 layer maximum normally located below 200 km. Any observations of the F2 -layer under G-conditions are possible either with topside ionospheric sounding [2] or Incoherent
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