Observations of vertical winds in the thermosphere with a Fabry-Perot Doppler imager at Syowa station, Antarctica

Abstract. Zenith-directed Fabry-Perot Spectrometer (FPS) and 3-Field Photometer (3FP) observations of the λ630 nm emission (~240 km altitude) were obtained at Davis station, Antarctica, during the austral winter of 1999. Eleven nights of suitable data were searched for significant periodicities common to vertical winds from the FPS and photo-metric variations from the 3FP. Three wave-like events were found, each of around one or more hours in duration, with periods around 15 minutes, vertical velocity amplitudes near 60 ms–1 , horizontal phase velocities around 300 ms–1 , and horizontal wavelengths from 240 to 400 km. These characteristics appear consistent with polar cap gravity waves seen by other workers, and we conclude this is a likely interpretation of our data. Assuming a source height near 125 km altitude, we determine the approximate source location by calculating back along the wave trajectory using the gravity wave property relating angle of ascent and frequency. The wave sources appear to be in the vicinity of the poleward border of the auroral oval, at magnetic local times up to 5 hours before local magnetic midnight.Key words. Meteorology and atmospheric dynamics (thermospheric dynamics; waves and tides)

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An optimised method for calculating the O<sup>+</sup>-O collision parameter from aeronomical measurements

Annales Geophysicae ◽

10.1007/s00585-995-0541-x ◽

1995 ◽

Vol 13 (5) ◽

pp. 541-550 ◽

Cited By ~ 10

Author(s):

C. J. Davis ◽

A. D. Farmer ◽

A. Aruliah

Keyword(s):

Collision Frequency ◽

Radar Data ◽

Data Sets ◽

High Latitudes ◽

Plasma Parameters ◽

Data Set ◽

F Region ◽

Fabry Perot ◽

Meridional Winds ◽

Vertical Winds

Abstract. A study has been made of the interaction between the thermosphere and the ionosphere at high latitudes, with particular regard to the value of the O+-O collision parameter. The European incoherent scatter radar (EISCAT) was used to make tristatic measurements of plasma parameters at F-region altitudes while simultaneous measurements of the neutral wind were made by a Fabry-Perot interferometer (FPI). The radar data were used to derive the meridional neutral winds in a way similar to that used by previous authors. The accuracy of this technique at high latitudes is reduced by the dynamic nature of the auroral ionosphere and the presence of significant vertical winds. The derived winds were compared with the meridional winds measured by the FPI. For each night, the value of the O+-O collision parameter which produced the best agreement between the two data sets was found. The precision of the collision frequency found in this way depends on the accuracy of the data. The statistical method was critically examined in an attempt to account for the variability in the data sets. This study revealed that systematic errors in the data, if unaccounted for by the analysis, have a tendency to increase the value of the derived collision frequency. Previous analyses did not weight each data set in order to account for the quality of the data; an improved method of analysis is suggested.

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Observations of thermospheric wind velocities and temperatures by the use of a Fabry–Perot Doppler imaging system at Syowa Station, Antarctica

Applied Optics ◽

10.1364/ao.34.008382 ◽

1995 ◽

Vol 34 (36) ◽

pp. 8382 ◽

Cited By ~ 22

Author(s):

Hideaki Nakajima ◽

Shoichi Okano ◽

Hiroshi Fukunishi ◽

Takayuki Ono

Keyword(s):

Imaging System ◽

Doppler Imaging ◽

Syowa Station ◽

Thermospheric Wind ◽

Fabry Perot ◽

Wind Velocities

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

Annales Geophysicae ◽

10.5194/angeo-28-549-2010 ◽

2010 ◽

Vol 28 (2) ◽

pp. 549-567 ◽

Cited By ~ 14

Author(s):

A. L. Aruliah ◽

E. M. Griffin ◽

H.-C. I. Yiu ◽

I. McWhirter ◽

A. Charalambous

Keyword(s):

Spatial Structure ◽

Spatial Scales ◽

Temperature Gradients ◽

Field Of View ◽

Doppler Broadening ◽

Doppler Imager ◽

Doppler Shifts ◽

Fabry Perot ◽

Thermospheric Winds ◽

Meso Scale

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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Vertical winds in the midlatitude thermosphere from Fabry-Perot interferometer measurements

Journal of Atmospheric and Terrestrial Physics ◽

10.1016/0021-9169(94)00102-t ◽

1995 ◽

Vol 57 (6) ◽

pp. 621-629 ◽

Cited By ~ 29

Author(s):

D.P. Sipler ◽

M.A. Biondi ◽

M.E. Zipf

Keyword(s):

Fabry Perot ◽

Vertical Winds

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Initial daytime and nighttime SOFDI observations of thermospheric winds from Fabry-Perot Doppler shift measurements of the 630-nm OI line-shape profile

Annales Geophysicae ◽

10.5194/angeo-29-1529-2011 ◽

2011 ◽

Vol 29 (9) ◽

pp. 1529-1536 ◽

Cited By ~ 16

Author(s):

A. J. Gerrard ◽

J. W. Meriwether

Keyword(s):

Multiple Point ◽

Thermospheric Wind ◽

Zonal Winds ◽

Doppler Imager ◽

Doppler Shifts ◽

Fabry Perot ◽

Wind Measurements ◽

Thermospheric Winds ◽

Night And Day ◽

The Cost

Abstract. In this paper we present both night and day thermospheric wind observations made with the Second-generation, Optimized, Fabry-Perot Doppler Imager (SOFDI), a novel triple-etalon Fabry-Perot interferometer (FPI) designed to make 24-h measurements of thermospheric winds from OI 630-nm emission. These results were obtained from the northeastern United States and from under the magnetic equator at Huancayo, Peru and demonstrate the current instrument capability for measurements of Doppler shifts for either night or day. We found the uncertainties in the measurements agree with expected values based upon forward modeling calculations; nighttime wind components having an uncertainty of ~20-m s−1 at 30-min resolution and daytime wind components having an uncertainty of ~70-m s−1 at 20-min resolution. The nighttime uncertainties are typically larger than those seen with traditional single-etalon FPIs, which occur at the cost of being able to achieve daytime measurements. The thermospheric wind measurements from Huancayo replicate recently reported CHAMP zonal winds and are in disagreement with current empirical wind climatologies. In addition, we discuss the incorporation of how multiple point heads in the SOFDI instrument will allow for unique studies of gravity wave activity in future measurements.

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Comparisons between Canadian prairie MF radars, FPI (green and OH lines) and UARS HRDI systems

Annales Geophysicae ◽

10.1007/s00585-997-1099-6 ◽

1997 ◽

Vol 15 (9) ◽

pp. 1099-1110 ◽

Cited By ~ 25

Author(s):

C. E. Meek ◽

A. H. Manson ◽

M. D. Burrage ◽

G. Garbe ◽

L. L. Cogger

Keyword(s):

Speed Ratio ◽

Short Term ◽

Canadian Prairie ◽

Canadian Prairies ◽

Wind Speeds ◽

Doppler Imager ◽

Radar Systems ◽

Fabry Perot ◽

Scatter Plots ◽

Relative Errors

Abstract. Detailed comparisons have been completed between the MF radars (MFR) in the Canadian prairies and three other systems: two ground-based Fabry-Perot interferometers (FPI) and the UARS high resolution Doppler imager (HRDI) system. The radars were at Sylvan Lake (52°N, 114°W), Robsart (49°N, 109°W) and the main continuing facility is at Saskatoon (52°N, 107°W). Statistical comparisons of hourly mean winds (1988-1992) for the Saskatoon MFR and FPI (557.7 nm green line) using scatter plots, wind speed-ratios, and direction-difference histograms show excellent agreement for Saskatoon. No serious biases in speeds or directions occur at the height of best agreement, 98 km. If anything, the MFR speeds appear bigger. The same applies to the Sylvan Lake MFR and Calgary FPI, where the best height is 88 km. In both cases these are close to the preferred heights for the emission layers. Differences between measurements seen on individual days are likely related to the influence of gravity waves (GW) upon the optical and radar systems, each of which have inherent spatial averaging (350, 50 km respectively), as well as the spatial difference between the nominal measurement locations. For HRDI, similar statistical comparisons are made, using single-overpass satellite winds and hourly means (to improve data quality) from MFR. Heights of best agreement, based upon direction-difference histograms, are shown; there is a tendency, beginning near 87 km, for these MFR heights to be 2 or 3 km greater than the HRDI heights. Speeds at these heights are typically larger for the satellite (MFR/HRDI = 0.7–0.8). Reasons for the differences are investigated. It is shown that the estimated errors and short-term (90 min) differences are larger for HRDI than for the MFR, indicating more noise or GW contamination. This leads to modest but significant differences in median speed-ratio (MFR/HRDI < 1). Also, comparison of the two systems is made under conditions when they agree best and when they show large disagreement. For the latter cases both systems show higher relative errors, and the HRDI vectors are frequently small. It is suggested that spatial or temporal GW wind fluctuations are the likely cause of the larger HRDI-MFR disagreement when wind speeds are small. No satisfactory explanation exists for the overall discrepancy in speeds between the MFR and HRDI.

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Thermospheric vertical winds in the auroral oval/polar cap region

Annales Geophysicae ◽

10.5194/angeo-20-1987-2002 ◽

2002 ◽

Vol 20 (12) ◽

pp. 1987-2001 ◽

Cited By ~ 6

Author(s):

P. A. Greet ◽

J. L. Innis ◽

P. L. Dyson

Keyword(s):

Auroral Oval ◽

Atmospheric Dynamics ◽

Polar Cap ◽

Frequency Distributions ◽

Meteorology And Atmospheric Dynamics ◽

Fabry Perot ◽

Thermospheric Winds ◽

Thermospheric Dynamics ◽

Vertical Winds ◽

Range Of Variation

Abstract. Thermospheric mean vertical winds from high-resolution Fabry-Perot Spectrometer observations of the l630 nm emission (from ~ 240 km altitude), over a four year interval 1997–2000, from Mawson (67.6° S, 62.9° E, Inv 70.5° S) and Davis (68.6° S, 78.0° E, Inv 74.6° S) are presented. Combining the four years of data shows Mawson mean hourly vertical winds vary between -10 ms-1 and +4 ms-1, while Davis mean hourly vertical winds vary between - 0 ms-1 and +10 ms-1. Mean hourly vertical winds from Mawson show little change with Kp, while at Davis the range of variation increases with increasing geomagnetic activity. Histograms of frequency distributions of such winds, and their variations with Kp and l630 nm emission intensity, are presented and discussed. Variations in mean hourly thermospheric winds and l630 nm emission intensities show at least three significant associations between mean vertical winds and the auroral oval. Mean vertical winds within the auroral oval are smaller than those outside the oval, particularly those in the polar cap. A downward wind associated with entry of the observing region into the auroral oval can be seen in both Mawson and Davis hourly mean vertical winds. Large vertical winds are seen poleward of the auroral oval/polar cap boundary, most significantly upward winds occur within ± 2 hr of magnetic midnight. Under moderately quiet geomagnetic conditions Davis passes through the auroral oval into the polar cap in the evening, but at higher Kp it passes into the polar cap earlier and larger, and more sustained mean vertical winds are observed.Key words. Meteorology and atmospheric dynamics (thermospheric dynamics)

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