Seasonal and Solar Variations of Absorption at Waltair

Abstract

Vertical incidence absorption measurements on 5·65 MHz taken during the period 1958–59 have been re-examined with a view to study the variation of absorption with solar activity and seasons. Assuming a linear relationship between 10·7 cm solar flux, taken as the index of solar activity, and the absorption figure D, significant correlation coefficient is obtained. The noontime absorption showed a stronger dependence on the 10·7 cm solar flux. Noon-time absorption measurements reduced to a constant solar flux and normalized to a constant cos χ showed a relative increase in equinoxes.