Total electron content of the ionosphere in middle latitudes

A study is made of measurements of the total electron content nT in the ionosphere, derived from satellite Doppler measurements. These are combined with simultaneous ionosonde measurements of the true height of Nmax and the electron content below Nmax. The following are the principal results obtained, nT varies diurnally, and at night it decays approximately exponentially with a mean effective attachment coefficient of 0.8×10−4 sec−1. The daytime maximum electron content was greater in winter than in summer in 1961–1962, but the difference was much less than in 1958–1960. The daytime electron content increases with the 10.7-cm solar radio noise flux S, and the rate of increase is greater in winter than in summer; a similar result holds over a large part of the solar cycle. The equivalent slab thickness, nT/Nmax is greater in daytime and in summer and increases with S. The ratio of the electron contents na/nb above and below hm is about 1.8 in the daytime, increases after sunset and before sunrise, and has a minimum in the middle of the night.