Upper thermospheric neutral wind and temperature measurements from an extended spatial field

Griffin, E. M.; Aruliah, A. L.; McWhirter, I.; Yiu, H.-C. I.; Charalambous, A.; McCrea, I. W.

doi:10.5194/angeo-26-2649-2008

Cited by 15 publications

(18 citation statements)

References 18 publications

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“…Recently, Griffin et al (2008) obtained the thermospheric winds and temperatures on 15 March 2007 (low solar activity) from the oxygen 630-nm emisson observations with a Scanning Doppler Imager (SCANDI). They showed mesoscale thermospheric structures which would result from particle precipitation, Joule heating, and other effects.…”

Section: Discussionmentioning

confidence: 99%

Morphological features and variations of temperature in the upper thermosphere simulated by a whole atmosphere GCM

Fujiwara

Miyoshi

2010

Ann. Geophys.

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Abstract. In order to illustrate morphological features and variations of temperature in the upper thermosphere, we performed numerical simulations with a whole atmosphere general circulation model (GCM) for the solar minimum and geomagnetically quiet conditions in March, June, September, and December. In previous GCMs, tidal effects were imposed at the lower boundaries assuming dominant diurnal and semi-diurnal tidal modes. Since the GCM used in the present study covers all the atmospheric regions, the atmospheric tides with various modes are generated within the GCM. The global temperature distributions obtained from the GCM are in agreement with ones obtained from NRLMSISE-00. In addition, the GCM also represents localised temperature structures which are superimposed on the global day-night distributions. These localised structures, which vary from hour to hour, would be observed as variations with periods of about 2-3 h at a single site. The amplitudes of the 2-3 h variations are significant at high-latitude, while the amplitudes are small at low-latitude. The diurnal temperature variation is more clearly identified at lowlatitude than at high-latitude. When we assume the same high-latitude convection electric field in each month, the temperature calculated in the polar cap region shows diurnal variation more clearly in winter than in summer. The midnight temperature maximum (MTM), which is one of the typical low-latitude temperature structures, is also seen in the GCM results. The MTMs in the GCM results show significant day-to-day variation with amplitudes of several 10s to about 150 K. The wind convergence and stream of warm air are found around the MTM. The GCM also represent the meridional wind reversals and/or abatements which are caused due to local time variations of airflow pattern in the low-latitude region.

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Section: Discussionmentioning

confidence: 99%

Morphological features and variations of temperature in the upper thermosphere simulated by a whole atmosphere GCM

Fujiwara

Miyoshi

2010

Ann. Geophys.

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“…Ongoing development of all-sky imaging Fabry-Perot spectrometers (Rees and Greenaway, 1983;Rees et al, 1984;Batten et al, 1988;Sekar et al, 1993;Biondi et al, 1995;Griffin et al, 2008) has resulted in instruments capable of recording independent spectra from many tens of locations across the sky simultaneously, making it possible to investigate this structure directly. F-region winds and temperatures have been observed previously from Mawson station, Antarctica, using a singleetalon, separation scanned, non-imaging ("pinhole scanner") Fabry-Perot spectrometer (Wardill et al, 1987;Conde and Dyson, 1995a,b;Innis et al, 1996;Greet et al, 1999).…”

Section: Introductionmentioning

confidence: 99%

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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“…As a consequence the temperatures were characteristic of a lower altitude and hence lower temperatures were measured during the precipitation. This has been proposed as the reason for anomalous low temperatures measured using the 557.7 nm emission by Holmes et al (2005) and for 630 nm by Griffin et al (2008). On comparing the SCANDI temperatures with the FPI, Fig.…”

Section: Scandi In Fixed Etalon Gap Mode and Very High Spatial Resolumentioning

confidence: 99%

“…Case studies for the nights 15 March 2007 and 4 December 2007 are described in detail in Griffin et al (2008Griffin et al ( , 2009. In these papers the ionosphere over Svalbard is probed using the IM-AGE magnetometer chain and CUTLASS radars to reveal the horizontal spatial distribution of a highly localised disturbance, and the ESR radars to show the vertical and temporal structure at high resolution.…”

Section: Case Studies Of Highly Localised Structure Using Scandimentioning

confidence: 99%

SCANDI – an all-sky Doppler imager for studies of thermospheric spatial structure

et al. 2010

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Abstract.A new all-sky Fabry-Perot Interferometer called the Scanning Doppler Imager (SCANDI) was built and installed at Longyearbyen in December 2006. Observations have been made of the Doppler shifts and Doppler broadening of the 630 nm airglow and aurora, from which upper thermospheric winds and temperatures are calculated. SCANDI allows measurements over a field-of-view (FOV) with a horizontal radius of nearly 600 km for observations at an altitude of 250 km using a time resolution of 8 min. The instrument provides the ability to observe thermospheric spatial structure within a FOV which overlaps that of the EISCAT Svalbard radar and CUTLASS SuperDARN radars. Coordinating with these instruments provides an important opportunity for studying ion-neutral coupling. The all-sky image is divided into several sectors to provide a horizontal spatial resolution of between 100-300 km. This is a powerful extension in observational capability but requires careful calibration and data analysis, as described here. Two observation modes were used: a fixed and a scanning etalon gap. SCANDI results are corroborated using the Longyearbyen single look direction FPI, and ESR measurements of the ion temperatures. The data show thermospheric temperature gradients of a few Kelvins per kilometre, and a great deal of meso-scale variability on spatial scales of several tens of kilometres.

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Upper thermospheric neutral wind and temperature measurements from an extended spatial field

Cited by 15 publications

References 18 publications

Morphological features and variations of temperature in the upper thermosphere simulated by a whole atmosphere GCM

Morphological features and variations of temperature in the upper thermosphere simulated by a whole atmosphere GCM

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

SCANDI – an all-sky Doppler imager for studies of thermospheric spatial structure

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