Measurements of the vertical column emission rates of atomic oxygen emissions from radiative recombination, ion-ion recombination, and dissociative recombination in the nighttime F region are sufficient to remotely sense the F layer height and peak plasma density. For example, measurements can be made of O I 1356 ¿ and [O I> 6300 ¿, with vertical column emission rates J1356 and J6300. To a very good approximation the peak electron density is proportional to (J1356)1/2, and second-order dependence on height and exospheric temperature is very small. To a good approximation the ratio (J1356)1/2/J6300 is a single-valued function of the layer height.