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back to earth is known as the critical frequency, and has a definite diurnal variation.
The graphs of the E and F1 critical frequencies are symmetrical about the noon axis. This is not true of the F2 critical frequency, which, moreover, is much more variable.
Comparison of the seasonal variations of the noon critical frequency and virtual height of the Fz region indicates that high values of critical frequency are accompanied by low virtual heights and vice versa.
Two maxima of critical frequency appear each year, approximately in February and November.
Low critical frequencies are predominant in the summer.
The seasonal variation of F2 virtual height is similar to the seasonal variation of the horizontal component of the earth's magnetic field.
Annual averages of the noon critical frequencies show a good correlation with annual average sunspot numbers.
Critical frequencies of the Fz region at midnight appear to be decreased by the occurrence of magnetic disturbances, especially in the summer.
OF AIR BY LENARD RAYS.
๐ SIMILAR VOLUMES
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