Comparison of Data on the Ionosphere, Sunspots, and Terrestrial Magnetism

Ionosphere data of the National Bureau of Standards from 1930 to 1935 are compared with data on the earth's magnetic field intensity and sunspot numbers. Seasonal variation of F
2
critical frequency and virtual height are compared with sunspot numbers and magnetic activity. Correlation of annual averages of the ionosphere critical frequencies with sunspot numbers is shown. Variations of midnight F
2
critical frequencies are compared with variations of sunspot numbers and magnetic activity.