Thermospheric winds and temperatures above Mawson, Antarctica, observed with an all-sky imaging, Fabry-Perot spectrometer

摘要

A new all-sky imaging Fabry-Perot spectrometer has been installed at Mawson station(67°36' S, 62°52' E), Antarctica. This instrument is capable of recordingindependent spectra from many tens of locations across the sky simultaneously. Useful operationbegan in March 2007, with spectra recorded on a total of 186 nights. Initial analysis has focusedon the large-scale daily and average behavior of winds and temperatures derived from observationsof the 630.0 nm airglow line of atomic oxygen, originating from a broad layer centered around240 km altitude, in the ionospheric F-region.The 1993 Horizontal Wind Model (HWM93), NRLMSISE-00 atmospheric model, and the CoupledThermosphere/Ionosphere Plasmasphere (CTIP) model were used for comparison. During thegeomagnetically quiet period studied, observed winds and temperatures were generally well modelled,although temperatures were consistently higher than NRLMSISE-00 predicted, by up to 100 K. CTIPtemperatures better matched our data, particularly later in the night, but predicted zonal windswhich were offset from those observed by 70–180 ms−1 westward. During periods of increasedactivity both winds and temperatures showed much greater variability over time-scales of less thanan hour. For the active night presented here, a period of 45 min saw wind speeds decrease byaround 180 ms−1, and temperatures increase by approximately 100 K. Active-period winds werepoorly modelled by HWM93 and CTIP, although observed median temperatures were in better agreementwith NRLMSISE-00 during such periods.Average behavior was found to be generally consistent with previous studies of thermospheric windsabove Mawson. The collected data set was representative of quiet geomagnetic and solar conditions.Geographic eastward winds in the afternoon/evening generally continued until around localmidnight, when winds turned equatorward. Geographic meridional and zonal winds in the afternoonwere approximately 50 ms−1 weaker than expected from HWM93, as was the transition toequatorward flow around midnight. There was also a negligible geographic zonal component to thepost-midnight wind where HWM93 predicted strong westward flow. Average temperatures between 19:00and 04:00 local solar time were around 60 K higher than predicted by NRLMSISE-00.