Evidence for the Effect of Corpuscular Radiation on the Ionosphere

Abstract

The correlation of maximum electron density in the F region at noon with solar activity is investigated for both long-term and month-to-month variations, in data for 1937–57 from all existing observatories. On the basis of noon-equilibrium between electron loss and ion production by solar radiation, an ionizing effect, strongly dependent on solar activity and peaked at latitudes of 55 to 65 deg is shown to exist. This latitudinal variation suggests a corpuscular origin of the effect. The possible source of a corpuscular flux is discussed. The energy of the ionizing particles is in the range of kev. Quantitative evidence is given that Van Allen belts could be an important, or possibly the main, source.