Equatorial spread F in relation to post‐sunset height changes and magnetic activity

Equatorial spread F, magnetic activity, and post-sunset rise in h′F are studied in detail as three parameters, and correlations in the variations in each of the three pairs are examined for all the seasons. Partial correlations are sought to examine the independent influence of magnetic activity and h′F changes on spread F. It is observed that the time of maximum spread F on each night is effectively controlled by the magnitude of the h′F change between 1800 and 1900 LT. The results are discussed in the light of the recent theory of spread F outlined by Martyn.