Thermospheric winds in the auroral oval: Observations of small scale structures and rapid fluctuations by a Doppler Imaging System

Batten, Simon; Rees, D.

doi:10.1016/0032-0633(90)90074-z

Cited by 17 publications

(8 citation statements)

References 17 publications

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“…Subsequently, a small number of other groups built similar instruments (e.g. Biondi et al, 1995). However, the analysis of the data is very time-consuming owing to the problems of image distortion by aberrations of the lens or detectors.…”

Section: Direct Measurements Of Neutral Winds By Wide-angle Imagersmentioning

confidence: 99%

Evidence of meso-scale structure in the high-latitude thermosphere

Aruliah

Griffin

2001

Ann. Geophys.

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Abstract. There is a widely held assumption that the thermospheric neutral gas is slow to respond to magnetospheric forcing owing to its large inertia and therefore, may be treated as a steady state background medium for the more dynamic ionosphere. This is shown to be over simplistic. The data presented here compare direct measurements of the thermospheric neutral winds made in Northern Scandinavia by Fabry-Perot Interferometers (FPIs) with direct measurements of the ionosphere made by the EISCAT radar and with model simulations. These comparisons will show that the neutral atmosphere is capable of responding to ionospheric changes on meso-scale levels, i.e., spatial and temporal scale sizes of less than a few hundred kilometres and tens of minutes, respectively.

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Section: Direct Measurements Of Neutral Winds By Wide-angle Imagersmentioning

confidence: 99%

Evidence of meso-scale structure in the high-latitude thermosphere

Aruliah

Griffin

2001

Ann. Geophys.

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“…A conventional FPI measures the shift in radius of the fringe (by a few pixels), which is superimposed on a small area of sky (typically 1 • field-of-view). For a Doppler imager with a fixed etalon gap, several fringes are mapped onto the whole sky and Doppler shifts are determined by measuring the radial displacement of segments of the ring pattern (Batten and Rees, 1990). Here the winds and temperatures can be found only for those segments of the sky that correspond to peaks in fringe intensity.…”

Section: Scandi Control Softwarementioning

confidence: 99%

“…Consequently there are few papers in existence compared with the FPI workhorse (e.g. Batten and Rees., 1990;Biondi et al, 1995).…”

Section: Introductionmentioning

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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“…Despite the thermosphere's very high kinematic viscosity, all-sky imaging FPI observations (Conde and Smith, 1998, for example) have observed relatively small scale structure in the wind field. Using a Doppler Imaging Fabry-Perot spectrometer Batten and Rees (1990) reported observations of structures in the F-region wind field at spatial scales as short as ∼50 km, with temporal scales as short as ∼10 min. They concluded that a spatial resolution much better than 500 horizontal km is required to resolve the smallest scale wind features that occur.…”

Section: Introductionmentioning

confidence: 99%

Numerical simulations of thermospheric dynamics: divergence as a proxy for vertical winds

2009

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Abstract.A local scale, time dependent three-dimensional model of the neutral thermosphere was used to test the applicability of two previously published empirical relations between thermospheric vertical wind and velocity divergence, i.e., those due to Burnside et al. (1981) and Brekke (1997). The model self-consistently solves for vertical winds driven by heat and momentum deposited into the neutral atmosphere by high latitude ion convection. The Brekke condition accurately mimicked the overall "shape" of the three-dimensional model vertical wind field although, as written, it consistently overestimated the vertical wind magnitude by a factor of approximately 5/3, for the heating scenarios that we considered. This same general behavior was observed regardless of whether the forcing was static or rapidly changing with time. We discuss the likely reason for the Brekke condition overestimating the magnitude of our vertical winds, and suggest an alternative condition that should better describe vertical winds that are driven by local heating. The applicability of the Burnside condition was, by contrast, quite variable. During static heating, both the magnitude and the sign of the model vertical winds were predicted reliably at heights above those of maximum energy and momentum deposition per unit mass. However, below the thermal forcing, the Burnside condition predicted vertical winds of the wrong sign. It also introduced significant artefacts into the predicted vertical wind field when the forcing changed suddenly with time. If these results are of general applicability (which seems likely, given the way these relations are derived) then the Burnside condition could usually be used safely at altitudes above h m F 2 . But it should be avoided below this height at all times, and even at high altitudes during periods of dynamic forcing. While the Brekke condition (or our modified version of it) could likely be used in all circumCorrespondence to: S. L. Cooper (sl7cooper@students.latrobe.edu.au) stances, there are few experimental scenarios for which this would be useful. This is because evaluation of the Brekke condition would not usually be possible unless the vertical wind was already known in advance.

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Thermospheric winds in the auroral oval: Observations of small scale structures and rapid fluctuations by a Doppler Imaging System

Cited by 17 publications

References 17 publications

Evidence of meso-scale structure in the high-latitude thermosphere

Evidence of meso-scale structure in the high-latitude thermosphere

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

Numerical simulations of thermospheric dynamics: divergence as a proxy for vertical winds

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