Some abnormalities in the variations of F₂-layer critical frequency during the period of high solar activity of solar cycle 8-19

Abstract

Some abnormalities in the variations of ƒoF2 were observed at Taipei during the period of very high solar activity of solar cycle 8–19. They are the saturation effect of ƒoF2 (i.e., the increasing rate of ƒ0F2 with respect to sunspot number is nearly zero at high solar activity), the occurrence of post-sunset peak of ƒoF2 and the increase in ƒoF2 during the ring eclipse. In this report variations of these phenomena are described, the close relationship existing among them is examined, and a probable explanation is given.