Sounding Rocket Observation of Nitric Oxide in the Polar Night.

Autor: Bailey, Scott M., McClintock, William E., Carstens, Justin N., Thurairajah, Brentha, Das, Saswati, Randall, Cora E., Harvey, V. Lynn, Siskind, David E., Stevens, Michael H., Venkataramani, Karthik
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Zdroj: Journal of Geophysical Research. Space Physics; Jun2022, Vol. 127 Issue 6, p1-14, 14p
Abstrakt: An altitude profile of Nitric Oxide (NO) in the 80–110 km altitude range was measured in the polar night from a sounding rocket on 27 January 2020. The observations were made using the technique of stellar occultation with a UV spectrograph observing the γ (1,0) band of NO near 215 nm. The tangent point for the altitude profile was at 74° latitude, a location that had been in darkness for 80 days. The retrieved slant column density profile is interpreted using an assumed four‐parameter analytic profile shape. Retrievals of the fitting parameters yield a profile with a peak NO concentration of 2.2 ± 0.7 × 108 cm−3 at 93.5 ± 4.1 km. The observations were made during a time of minimum solar and geomagnetic activity. The NO maximum retrieved from the rocket profile is significantly larger in abundance and lower in altitude than other observations on the same day at nearby latitudes just outside the polar night. These rocket‐borne results are consistent with NO that is created over the course over the polar winter and is confined to high latitudes in the polar night by the mesospheric polar vortex. During the course of that confinement the abundance increases due to the lack of photodissociation, allowing the NO to descend. We show that the observed descent can be explained by eddy diffusion‐driven transport, though vertical advection cannot be ruled out. Plain Language Summary: A sounding rocket is used to obtain an altitude profile of Nitric Oxide (NO) in the polar night. The measurement is performed by observing the attenuation of light from a star by NO. The location of the observation had been in darkness for 80 days. This long duration is important because in the absence of sunlight, NO lasts longer in the atmosphere and therefore has more time to grow to a greater abundance and to descend to lower altitudes. We find that the observed polar night NO is larger in abundance than most previous observations of NO outside the polar night, even though the level of solar activity which creates NO was at a minimum. We also find that the maximum NO density is observed at a lower altitude than many previous measurements. We show that the observed descent of NO is consistent with that caused by turbulent mixing in the atmosphere, though we cannot rule out the possible role of vertical winds. Key Points: The altitude profile of Nitric Oxide (NO) in the mesosphere and lower thermosphere was made from a sounding rocket in polar night conditionsThe NO density, observed at very low solar activity, was larger in abundance and at a lower altitude than most non‐polar night observationsThe observed NO profile is consistent with NO produced above 100 km and then transported, likely by eddy diffusion, to the upper mesosphere [ABSTRACT FROM AUTHOR]
Databáze: Complementary Index
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