Effects of conjugate point sunrise in the topside ionosphere deduced from Alouette 1 records

Abstract

Using electron density scale heights deduced from Alouette 1 data for the three winters 1962–1964, an attempt has been made to detect a conjugate point heating effect in the height range 500–900 km. Although the dominant feature of the data is the variation of the scale height with latitude, it is possible to observe increases due to conjugate photoelectrons heating. The observed increases are smaller and shorter than those expected on the basis of the temperature increases reported by other workers, as the curve for the variation of scale height with solar zenith angle at the conjugate point ( χ c ) tends towards a maximum around χ c = 98°. Theoretical calculations and practical results from the incoherent scatter facility at St Santin-Nancay indicate that vertical temperature gradients are responsible for these effects.