Sounding Rocket Observation of Lower Thermospheric Nitric Oxide in the Polar Night

Abstract:

There is strong evidence that Nitric Oxide (NO) is a key coupling agent by which the magnetosphere channels solar energy into the polar winter upper atmosphere. NO is produced through a chain of events that begins with energetic particle precipitation (EPP), typically in the lower thermosphere. When NO is transported to lower altitudes, it participates in catalytic reactions that destroy ozone. Such transport becomes possible in the polar night where destruction of NO by photodissociation is not possible. While NO has long been understood as an important species in the upper atmosphere, its highly variable abundance throughout the thermosphere has primarily been measured during sunlit conditions. The relative lack of nighttime measurements is a crucial gap in our knowledge as there is a large and rapidly growing body of evidence that NO created by energetic precipitating particles EPP, after being transported to the lower atmosphere during polar night, has a significant and potentially long-term effect on stratospheric ozone distributions.

A January 27, 2020 sounding rocket mission measured a lower thermospheric NO profile using stellar occultation. A moderately high-resolution spectral measurement of the NO gamma-bands near 215 nm was made while viewing the limb during the downleg segment of the rocket flight. Column NO densities were obtained from the observed atmospheric transmission and were used to calculate the volume density profile. In this talk we will discuss the observations and their interpretation as well as comparisons with other relevant datasets.