On the physical mechanism of the ionospheric storms in the F2-layer

AE-C satellite data on the neutral thermospheric composition and temperature along with the ground-based ionospheric sounding data at Winnipeg, Boulder and Havana were used to analyze the physical mechanism of F2-layer parameter variations during the ionospheric storm on 25 Jan 1974. Rishbeth's isobaric F2-layer concept concerning a negative F2-layer storms is analyzed. The observed negative as well as positive n e m F2 variations during 25 Jan 1974 storm period may be explained within the scope of the current F2-region theory without taking into account additional processes proposed by Rishbeth.