Book excerpt: 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.