Simultaneous measurements of ionospheric parameters at the dip equator

Results are presented of simultaneous measurements of ion composition, neutral composition and electron density from two rocket flights made from Thumba-one by day and the other at night. The data are used to derive the electron temperature at different altitudes by equating the ionization and recombination rates. The electron temperature during the midday flight is observed to be the same as the neutral temperature around 150 km, while at 110 km it is twice as large as the neutral temperature. At night it is suggested that the Lyman-beta radiation is sufficient to account for the observed ionization at the E-region level. A diurnal variation in the nitric oxide concentration at E-region altitudes is also indicated by larger values at night than during the day