Аннотация
This study reports observations of the response of the mid-latitude ionospheric F-layer to the passage of the atmospheric gravity wave (AGW) produced by the July 2004 geomagnetic storm, using data from the ground ionosonde located at Alma-Ata (43.25°N, 76.92°E). Ionograms were recorded every 5 min. They were analysed for temporal variations of virtual heights of specific frequencies (the virtual heights of a constant electron density), critical frequencies of the F-layer (fo,xF) and height profiles of the electron density (N(h)-profiles). The temporal behaviour of all F-layer parameters such as the altitude of its peak (hmF), the electron density at the peak (NmF) and the half thickness of the layer (ΔhF) revealed well-defined wave structures throughout the entire night of 24-25 July 2004. A comprehensive understanding of the relationship between phases of various parameters of the F-layer is established. It is shown that the relationship between phases of hmF, NmF and ΔhF variations is determined by the value of the wave front tilt. As a rule, the certain phase of ΔhF precedes that of hmF, and NmF anticorrelates with ΔhF. Last result contrast with previous investigations, which have frequently assumed a negative correlation between NmF and hmF. A small amplitude of NmF variations compared with N(t) at certain altitudes may be largely explained in terms of the height gradient of AGW amplitudes.