ATMOS observations of nitric oxide in the mesosphere and lower thermosphere

The nitric oxide density in the Earth's atmosphere between 50 and 130 km was measured by the ATMOS (Atmospheric Trace Molecule Spectroscopy) experiment onboard the Spacelab 3 mission on April 30, 1985 and May 1, 1985, Three observations were made at geographic latitudes of 35 degrees N, 34 degrees N, and 29 degrees N which correspond to geomagnetic latitudes of 26 degrees N, 44 degrees N, and 39 degrees N. The ATMOS measurements of nitric oxide in the thermosphere were compared to SME measurements made during the same time period. The two techniques agree within the geophysical variability of thermospheric nitric oxide. The observations show that during a geomagnetic storm there is a strong latitudinal gradient in the nitric oxide density in the lower thermosphere. Comparison of the observations with a one-dimensional time-dependent model shows that at midlatitudes, nitric oxide is transported downward from the thermosphere into the mesosphere as low as 70 km but not downward into the stratosphere.