Thermospheric horizontal winds above Mawson, Antarctica

Conde, M.; Dyson, P. L.

doi:10.1016/0273-1177(95)00171-a

Cited by 10 publications

(6 citation statements)

References 21 publications

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“…The Mawson-to-Davis bearing is approximately 30°east of the corrected geomagnetic (CGM) south direction from Mawson; thus the Mawson-Davis great circle direction is close to being geomagnetically north-south aligned. The common volume observations therefore indicated an increasing magnetic meridional wind throughout both nights, consistent with the horizontal wind flow estimated by each instrument individually (see Figure 9 (top) for Mawson SDI horizontal winds) and also with previous observations above Mawson [Jones et al, 1987;Conde and Dyson, 1995a;Smith et al, 1998;Greet et al, 1999;Anderson et al, 2009].…”

Section: Resultssupporting

confidence: 89%

Spatial sampling of the thermospheric vertical wind field at auroral latitudes

et al. 2011

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[1] Results are presented from two nights of bistatic Doppler measurements of neutral thermospheric winds using Fabry-Perot spectrometers at Mawson and Davis stations in Antarctica. A scanning Doppler imager (SDI) at Mawson and a narrow-field Fabry-Perot spectrometer (FPS) at Davis have been used to estimate the vertical wind at three locations along the great circle joining the two stations, in addition to the vertical wind routinely observed above each station. These data were obtained from observations of the 630.0 nm airglow line of atomic oxygen, at a nominal altitude of 240 km. Low-resolution all-sky images produced by the Mawson SDI have been used to relate disturbances in the measured vertical wind field to auroral activity and divergence in the horizontal wind field. Correlated vertical wind responses were observed on a range of horizontal scales from ∼150 to 480 km. In general, the behavior of the vertical wind was in agreement with earlier studies, with strong upward winds observed poleward of the optical aurora and sustained, though weak, downward winds observed early in the night. The relation between vertical wind and horizontal divergence was seen to follow the general trend predicted by Burnside et al. (1981), whereby upward vertical winds were associated with positive divergence and vice versa; however, a scale height approximately 3-4 times greater than that modeled by NRLMSISE-00 was required to best fit the data using this relation.

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Section: Resultssupporting

confidence: 89%

Spatial sampling of the thermospheric vertical wind field at auroral latitudes

et al. 2011

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“…The average winds presented here are similar to those found in comparable studies of thermospheric winds above Mawson, see for example Conde and Dyson (1995a). However, in this earlier study, strong (100-200 ms −1 ) average winds were observed flowing geomagnetically equatorward after 02:50 local solar time (magnetic midnight), whereas the average data presented here show very weak flow in this time sector, directed magnetically eastward.…”

Section: Average Daily Behaviorsupporting

confidence: 89%

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

et al. 2009

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Abstract.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 recording independent spectra from many tens of locations across the sky simultaneously. Useful operation began in March 2007, with spectra recorded on a total of 186 nights. Initial analysis has focused on the large-scale daily and average behavior of winds and temperatures derived from observations of the 630.0 nm airglow line of atomic oxygen, originating from a broad layer centered around 240 km altitude, in the ionospheric F-region.The 1993 Horizontal Wind Model (HWM93), NRLMSISE-00 atmospheric model, and the Coupled Thermosphere/Ionosphere Plasmasphere (CTIP) model were used for comparison. During the geomagnetically 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. CTIP temperatures better matched our data, particularly later in the night, but predicted zonal winds which were offset from those observed by 70-180 ms −1 westward. During periods of increased activity both winds and temperatures showed much greater variability over time-scales of less than an hour. For the active night presented here, a period of 45 min saw wind speeds decrease by around 180 ms −1 , and temperatures increase by approximately 100 K. Activeperiod winds were poorly modelled by HWM93 and CTIP, although observed median temperatures were in better agreement with NRLMSISE-00 during such periods.Average behavior was found to be generally consistent with previous studies of thermospheric winds above Mawson. The collected data set was representative of quiet geomagnetic and solar conditions. Geographic eastward windsCorrespondence to: C. Anderson (c.anderson@latrobe.edu.au) in the afternoon/evening generally continued until around local midnight, when winds turned equatorward. Geographic meridional and zonal winds in the afternoon were approximately 50 ms −1 weaker than expected from HWM93, as was the transition to equatorward flow around midnight. There was also a negligible geographic zonal component to the post-midnight wind where HWM93 predicted strong westward flow.

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“…There is a large body of λ630 nm FPS observations of the westward jet stream in the F region, although such westward wind is almost never seen at these heights under magnetically quiet conditions [ Wardill et al , 1987; Sica et al , 1986; Aruliah et al , 1991a, 1991b; Conde and Dyson , 1995b; Niciejewski et al , 1996, Conde and Smith , 1998]. It was thus something of a surprise for us to observe such well developed westward flow on a quiet night at 150 km altitude.…”

Section: Discussionmentioning

confidence: 97%

The HEX experiment: Determination of the neutral wind field from 120 to 185 km altitude near a stable premidnight auroral arc by triangulating the drift of rocket‐deployed chemical trails

Wescott¹,

Stenbaek‐Nielsen²,

Conde³

et al. 2006

J. Geophys. Res.

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[1] On 25 March 2003, Horizontal E-Region Experiment (HEX) released trimethyl aluminum trails from two rockets launched northward from Poker Flat Research Range near Fairbanks to map the vertical wind field near a stable premidnight auroral arc system. They deployed three trails of trimethyl aluminum chemical ''puffs,'' whose subsequent motion traced the prevailing wind field. This motion was determined using triangulation from four ground observation sites. Position and speed accuracies were estimated to be $1 km and a few meters per second, respectively. The first rocket followed a novel flat trajectory; it released a nearly horizontal trail of length 200 km, at an average altitude of $145 km. The second rocket was launched 19 min later and released two trails between 125 and 175 km altitude along a conventional steep trajectory. All puffs between 130 and 175 km altitude drifted geomagnetic westward, almost exactly parallel to the aurora. From prior observations and modeling, we had expected to observe convective upwelling near the arcs. We did not; vertical winds were essentially downward throughout the horizontal trail, with speeds between 0 and 20 m s À1 . Although an abatement of downward flow was observed $40 km equatorward of the arcs, these data alone do not establish a causal relationship between the abatement and the arcs. Vertical speeds of 20 m s À1 are relatively modest. However, because the observed wind field would entrain air parcels in flow parallel to the arc system, even vertical speeds around 15 m s À1 could displace individual air parcels by several scale heights if they occurred all along the arcs.

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Thermospheric horizontal winds above Mawson, Antarctica

Cited by 10 publications

References 21 publications

Spatial sampling of the thermospheric vertical wind field at auroral latitudes

Spatial sampling of the thermospheric vertical wind field at auroral latitudes

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

The HEX experiment: Determination of the neutral wind field from 120 to 185 km altitude near a stable premidnight auroral arc by triangulating the drift of rocket‐deployed chemical trails

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