Photoionization heating in theFregion of the atmosphere

The thermal economy in the F region of the atmosphere is investigated using the the barometric equation and the continuity equation for thermal energy. It is concluded that photoionization is certainly a major source, and possibly the predominant source, of F-region heating. The assumptions and approximations are discussed and are shown not to invalidate the conclusion. The heat flux due to photoionization in the F region at low and middle latitudes at sunspot maximum is estimated to lie between 0.5 and 2.0 ergs/cm2 sec, with a most probable value of about 1.0 erg/cm2 sec.