Worldwide atmospheric gravity-wave study in the European sector 1985–1990

Williams, P. J. S.; Virdi, T. S.; Lewis, R. V.; Lester, M.; Rodger, A. S.; McCrea, I. W.; Freeman, K. S. C.

doi:10.1016/0021-9169(93)90014-p

Cited by 44 publications

(36 citation statements)

References 11 publications

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“…3.3, and observations of TIDs in EISCAT data are discussed in e.g. Williams et al (1993), Lanchester et al (1993), Shibata and Schlegel (1993), Mitchell and Howells (1998). Figure 3 shows the 630.0 nm intensities from the tristatic campaign on the 25 November 2003.…”

Section: Thermospheric Datamentioning

confidence: 93%

“…At higher altitudes, AGWs are important as they can transport energy and momentum large distances, for example, redistributing energy to equatorial latitudes. However, most highlatitude studies have been on Travelling Ionospheric Disturbances (TIDs), the ionospheric reaction to AGWs (see for example Balthazor and Moffett, 1999;MacDougall et al;Arnold et al, 1998, and reviews by Hunsucker, 1982;Williams et al, 1993;Hocke and Schlegel, 1996). Gravity waves have been observed in the upper thermosphere over the southern polar cap, for example, by de Deuge et al (1994) and with photometer observations of the 630.0 nm oxygen emissions and by Innis and Conde (2002) in satellite data.…”

Section: Introductionmentioning

confidence: 99%

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Thermospheric gravity waves in Fabry-Perot Interferometer measurements of the 630.0nm OI line

et al. 2006

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Abstract. Gravity waves are an important feature of mesosphere -lower thermosphere (MLT) dynamics, observed using many techniques and providing an important mechanism for energy transfer between atmospheric regions. It is known that some gravity waves may propagate through the mesopause and reach greater altitudes before eventually "breaking" and depositing energy. The generation, propagation, and breaking of upper thermospheric gravity waves have not been studied directly often. However, their ionospheric counterparts, travelling ionospheric disturbances (TIDs), have been extensively studied in, for example, radar data. At high latitudes, it is believed localised auroral activity may generate gravity waves in-situ. Increases in sensor efficiency of Fabry-Perot Interferometers (FPIs) located in northern Scandinavia have provided higher time resolution measurements of the auroral oval and polar cap atomic oxygen red line emission at 630.0 nm. A Lomb-Scargle analysis of this data has shown evidence of gravity wave activity with periods ranging from a few tens of minutes to several hours. Oscillations are seen in the intensity of the line as well as the temperatures and line of sight winds. Instruments are located in Sodankylä, Finland; Kiruna, Sweden; Skibotn, Norway, and Svalbard in the Arctic Ocean. A case study is presented here, where a wave of 1.8 h period has a phase speed of 250 ms −1 with a propagation angle of 302 • , and a horizontal wavelength of 1600 km. All the FPIs are colocated with EISCAT radars, as well as being supplemented by a range of other instrumentation. This allows the waves found in the FPI data to be put in context with the ionosphere and atmosphere system. Consequently, the source region of the gravity waves can be determined.

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Section: Thermospheric Datamentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Thermospheric gravity waves in Fabry-Perot Interferometer measurements of the 630.0nm OI line

et al. 2006

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“…This technique has been successfully applied using EISCAT and additional facilities at mid and low latitudes (Morgan, 1983;Crowley and McCrea, 1988;Rice et al, 1988;Williams et al, 1988Williams et al, , 1993). An important quantity for the propagation of TIDs/AGWs is the complete wave vector of the wave-like¯uctua-tions.…”

Section: Introductionmentioning

confidence: 99%

Case studies of the propagation characteristics of auroral TIDS with EISCAT CP2 data using maximum entropy cross-spectral analysis

Schlegel

1998

Ann Geophysicae

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Abstract. In this paper case studies of propagation characteristics of two TIDs are presented which are induced by atmospheric gravity waves in the auroral F-region on a magnetic quiet day. By means of maximum entropy cross-spectral analysis of EISCAT CP2 data, apparent full wave-number vectors of the TIDs are obtained as a function of height. The analysis results show that the two events considered can be classi®ed as moderately large-scale TID and mediumscale TID, respectively. One exhibits a dominant period of about 72 min, a mean horizontal phase speed of about 180 m/s (corresponding to a horizontal wavelength of about 780 km) directed south-eastwards and a vertical phase speed of 55 m/s for a height of about 300 km. The other example shows a dominant period of 44 min, a mean horizontal phase velocity of about 160 m/s (corresponding to a horizontal wavelength of about 420 km directed southwestwards, and a vertical phase velocity of about 50 m/s at 250 km altitude.

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“…Hedin and Mayr, 1987;Taylor and Edwards, 1991;Hines, 1993;Forbes et al, 1995) and on observations of plasma oscillations with incoherent scatter (IS) radars, HF and MF radars, ionosondes, and total electron contents when it was assumed that the plasma acts a passive tracer to display motions of the neutral atmosphere (e.g. Titheridge, 1968;Hajkowicz and Hunsucker, 1987;Rice et al, 1988;Hajkowicz, 1991;Williams et al, 1993;Manson et al, 1997). The observations also indicated that the propagation of traveling ionospheric disturbances is associated with atmospheric gravity waves (AGWs).…”

Section: Introductionmentioning

confidence: 99%

Effects of atmospheric oscillations on the field-aligned ion motions in the polar F-region

Oyama¹,

Nozawa²,

Buchert³

et al. 2000

Ann. Geophys.

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Abstract. The ®eld-aligned neutral oscillations in the F-region (altitudes between 165 and 275 km) were compared using data obtained simultaneously with two independent instruments: the European Incoherent Scatter (EISCAT) UHF radar and a scanning FabryPerot interferometer (FPI). During the night of February 8, 1997, simultaneous observations with these instruments were conducted at Troms , Norway. Theoretically, the ®eld-aligned neutral wind velocity can be obtained from the ®eld-aligned ion velocity and by di usion and ambipolar di usion velocities. We thus derived ®eld-aligned neutral wind velocities from the plasma velocities in EISCAT radar data. They were compared with those observed with the FPI (k 630:0 nm), which are assumed to be weighted height averages of the actual neutral wind. The weighting function is the normalized height dependent emission rate. We used two model weighting functions to derive the neutral wind from EISCAT data. One was that the neutral wind velocity observed with the FPI is velocity integrated over the entire emission layer and multiplied by the theoretical normalized emission rate. The other was that the neutral wind velocity observed with the FPI corresponds to the velocity only around an altitude where the emission rate has a peak. Di erences between the two methods were identi®ed, but not completely clari®ed. However, the neutral wind velocities from both instruments had peak-to-peak correspondences at oscillation periods of about 10±40 min, shorter than that for the momentum transfer from ions to neutrals, but longer than from neutrals to ions. The synchronizing motions in the neutral wind velocities suggest that the momentum transfer from neutrals to ions was thought to be dominant for the observed ®eld-aligned oscillations rather than the transfer from ions to neutrals. It is concluded that during the observation, the plasma oscillations observed with the EISCAT radar at di erent altitudes in the F-region are thought to be due to the motion of neutrals.

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Worldwide atmospheric gravity-wave study in the European sector 1985–1990

Cited by 44 publications

References 11 publications

Thermospheric gravity waves in Fabry-Perot Interferometer measurements of the 630.0nm OI line

Thermospheric gravity waves in Fabry-Perot Interferometer measurements of the 630.0nm OI line

Case studies of the propagation characteristics of auroral TIDS with EISCAT CP2 data using maximum entropy cross-spectral analysis

Effects of atmospheric oscillations on the field-aligned ion motions in the polar F-region

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