On the behavior of ƒ₀F₂during solar eclipses

In a recent paper [Evans, 1965] the suggestion was made that instances in which a total eclipse of the sun has caused an increase in ƒ0F2 can be explained as a consequence of downward diffusion of ionization from above hmaxF2. This suggestion was advanced on the basis of radar backscatter measurements made at the Millstone Observatory (42.6°N; 71.5°W) during the total eclipse of the sun on July 20, 1963. These measurements gave values for the electron density N, electron temperature Te, and ion temperature Ti over the approximate height interval of 220–750 km. It was found that at most heights there was a large decrease (∼ 1000°K) in the value of the electron temperature Te and a smaller decrease in the ion temperature Ti as a consequence of the eclipse.