TheERegion of the Ionosphere During the Total Solar Eclipse of October 1, 1940

It is pointed out that ionospheric observations during the total solar eclipse of October 1, 1940, visible in northern Brazil, may provide data for an exacting test of the theory of solar radiation origin of the $E$ region and may yield a precise value of the ionic recombination coefficient $\alpha$ that occurs in the theory. To this end $E$ region ionization curves are worked out for various assumed values of $\alpha$ during the eclipse.