Non-Seasonal Variation in the E-Layer Ionization

Abstract

SOME time ago, Shimazaki¹studied ƒoEas a function of cos χ for stations in many different locations using only noon values of ƒoEobtained during the International Geophysical Year. According to Chapman's theory, we should have : but Shimazaki puts : Kshould have a constant value all over the Earth, determined by the level of solar activity. Waldmeier and also Harnischmacher found, in 1944, that yis greater than 1.00; this shows that Chapman's theory is not completely valid, and that we must be cautious in preferring the exponent four in the first equation. The calculated values of K′ for many stations were used by Shimazaki to show that they tended to increase during the months November, December and January. This effect persists even if one corrects for the variations of solar activity and of the distance between the Sun and the Earth. Shimazaki explained his results by a hypothetical additional ionizing agent.