The role of enhanced chemical reaction rates in the formation of the daytime F-region trough is examined. A simple convection model is used to estimate the maximum likely elevation of effective temperature for the ion reaction O+ + N2 yields NO(+)+ N. Under extreme conditions the effective temperature can reach 4000 k resulting in a 30-fold increase in the reaction rate. However, the resulting reduction in F-region electron density is only a factor of 4. Under more usual conditions, the reduction is less than a factor of 2. The actual density reduction factor in the daytime trough is observed to vary between 3 and 10 under normal conditions. Therefore, we conclude that under most circumstances, convection-enhanced chemistry contributes very little to the formation of the daytime trough.

This is a compilation of seventeen (17) papers presented by the Space Physics Division at the 1978 Symposium on the Effect of the Ionosphere on Space and Terrestrial Systems. The symposium was jointly sponsored by the Naval Research Laboratory and the Office of Naval Research, January 24-26, 1978. The emphasis is on the occurrence of ionospheric irregularities and their effect on communication, radar and navigation systems.