NUMERICAL SIMULATION OF IONOSPHERIC STRUCTURE BELOW F2 PEAK
1994, 14 (2):
Taking account of the photo-chemical reactions and the transport processes induced by diffusion and neutral wind, a one-dimensional and time-dependent numerical model for the ionospheric profile is established, in which stable and metastable atomic ions [O+(4S), O+(2D) and O+(2P)]and molecular ions (O2+, NO+ and N2+) are involved. Based on the model, the ionospheric morphology and related processes at WUCHANG (30.5°N, 114.4°E) in the region below the F2 peak, especially. within the E/F and F1/F2 valleys, are discussed, and the main results are summarized as follows:(1) With respect to atomic ions, the chemical reactions and the transport process for O+(4S) only are responsible for a shallow F1/F2 valley; the O+(2D)Patticipated reactions are more favourable to form a deep one conversely, O+(2P), when present, is an unfavourable factor for ie valley formation. As for molecular ions, the transport induced by neutral wind is also beneficial for a deep valley. (2) The atomic-molecular ions transit level is located at about 180-190 km with a larger value for morning and evening hours only above which the linear assumption of the loss rate is valid in the traditional continuity epuation with respect to electrons.(3) The widest F1/F2 valley occurs at 11h (LT), and the deepest Due at local noon. The E/F valley width is generally about 20-30km for low solar activity and 25-45km for high one, and the morning and evening values are 10-20km larger. (4) O2+ with a double-peak profile is the most important composition in for ining Eand F1 ledges. Its low peak forms E-layer, while the upper one, in combination with NO+ contribution, makes up F1-Layer.Good agreements are found between the simulated and the observational results as a whole. The present model exhibits great potentiality for the study of ionospheric profiles, such as its mathematical description, the ionogram inversion techniques. and also the morphological and related mechanical research for a particular geophysical event.
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