Comment on “Nighttime Na D emission observed from a polar‐orbiting DMSP satellite” by A. L. Newman

In a recent paper, Newman [1988] has presented tor [Takahashi et al., 1989]. It is difficult to Na D airglow profiles obtained by a limb-scanning compare measurements made at different locations instrument aboard one of the DMSP satellites. and different times, but all the published data These profiles show a number of surprising fea-suggest that, at the most, the intensities should tures. The unexpected characteristics of the be similar at mid-northern latitudes and the satellite measurements are (1) surprisingly high equator in July, and more probably the equatorial intensities at the equator, as compared with mid-airglow would be weaker. northern latitudes; (2) topside scale heights for the emission intensity as large as 16 km; and (3) Topside Scale Heights peak emission heights as low as 75 km. The topside scale heights for the emission, Observations measured by the satellite, vary from just over 6 km near the equator to nearly 16 km at 50N. The Emission Intensities Typical values at mid-latitudes are 10 -12 km. Assuming that the Chapman mechanism is responsi-The measured intensities were about a factor ble for the excitation of the sodium atoms, then