The dayglow of the sodium D lines

Abstract : Observation of the sodium dayglow in the scattered sunlight observed on the surface of the earth with a magnetic scanning photometer is reported. The intensity (September to November 1960) is unexpectedly strong—30 kilorayleighs toward the zenith—and evidence is that during the period studied the amount of sodium is 4 times as large in the daytime as at twilight. However, a strong correlation is found between the dayglow and twilight intensities. The abundance can be as high as 40×10⁹ atoms/cm2. The possible role of water vapor absorption in the results is discussed.