SPEARS Seminar: Microwave Radiometry of the Antarctic Middle Atmosphere

Doctor David Newnham, British Antarctic Survey

Friday 12 October 2012, 1400-1500
B2 Physics Building

Odd nitrogen and odd hydrogen are generated by energetic electrons and protons in the polar middle atmosphere following geomagnetic storms. In the thermosphere and upper mesosphere NOx exists mainly as NO but below 65 km conversion to NO2 occurs. In darkness NOx has a sufficiently long lifetime to be transported downward by the high latitude winter-time polar vortex and perturb stratospheric ozone abundances. Satellite observations have shown the large-scale impacts of major solar proton storms on the polar stratosphere and mesosphere. However, NOx production by radiation-belt electrons is less well understood. Electrons in the range 10 keV to several MeV precipitate from the radiation belts in the subauroral zone at geomagnetic latitudes ≤ 75°, and particularly in the Southern hemisphere and pole-ward of the South-Atlantic Magnetic Anomaly (SMA).

In order to investigate NOx production by energetic electrons, transport in the polar vortex, and impacts on ozone a ground-based passive microwave radiometer has been developed. The instrument achieves a noise temperature of 200 K at 230 GHz and 250 GHz, allowing observations of the diurnal variability of nitric oxide (NO), ozone (O3), and carbon monoxide (CO) over the altitude range 35-85 km. In this talk I will present results obtained from Troll station, Antarctica (72°01' S 02°32' E, geomagnetic latitude 65°), a location equator-ward of the auroral zone, pole-ward of the area of radiation belt precipitation and the SMA, and deep within the polar vortex during the Austral winter. I will also discuss the forthcoming deployment of the BAS microwave radiometer at the Halley VI research station (75°35' S, 26°34' W, geomagnetic latitude 68°) and atmospheric model developments, as well as requirements for new measurements.