Interpretation of the shape factor at Ootacamund, India

The paper deals with equatorial ATS-6 measurements of the shape factor, F, interpreted in terms of the shape of the electron density profile along the ray path. The observed rapid increase in F at sunrise is attributed to EUV production of ionization in the E and F regions. The evening decrease is seen to result from an upward drift of the F region at sunset and the evening decay of the E and bottomside F regions. The nighttime peak, or plateau, is caused by gradual decrease of the electron density profile.