'Anomalous' Behaviour of the F₂ Region of the Ionosphere

Abstract

IT has been known for some years that the seasonal and diurnal variations, and the geographical distribution of the maximum electron density N in the F₂ layer, the main observable region of the ionosphere, are anomalous in that they do not conform to the simple Chapman theory of ionization production, according to which N should be proportional to cos χ ^½, where χ is the zenith distance of the sun. For example, in temperate and high latitudes in the northern hemisphere, the noon values of N show a minimum in mid-summer and a maximum in mid-winter, a variation which is exactly out of phase with theory; while in the southern hemisphere in temperate latitudes noon N exhibits maxima near the equinoxes and minima in mid-summer and mid-winter.