The generation and propagation of atmospheric gravity waves observed during the Worldwide Atmospheric Gravity-wave Study (WAGS)

Williams, P. J. S.; Crowley, G.; Schlegel, K.; Virdi, T. S.; McCrea, I. W.; Watkins, G.W; Wade, N. M.; Hargreaves, J. K.; Lachlan‐Cope, Tom; Müller, Heinz; Baldwin, John E.; Warner, P. J.; Eyken, A. P. van; Hapgood, M. A.; Rodger, A. S.

doi:10.1016/0021-9169(88)90018-9

Cited by 72 publications

(45 citation statements)

References 16 publications

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“…The dominance of Joule heating in the F-region for an enhanced electric ®eld is also compared to the deduction by Williams et al, (1988); from EISCAT incoherent scatter radar observations taken during a period of moderate electric ®eld disturbances (up to about 60 mV/m in a dominantly southward direction). Williams et al (1988) stated that`The Lorentz force is again dominant below 110 km, but the ratio vat is closer to unity at greater heights'.…”

Section: Model Descriptionmentioning

confidence: 94%

“…Williams et al (1988) stated that`The Lorentz force is again dominant below 110 km, but the ratio vat is closer to unity at greater heights'. It must be noted however that Williams et al (1988) calculated vat using Brekke's (1979) formula, and inserting observed values of the parameters.…”

Section: Model Descriptionmentioning

confidence: 99%

“…In summary, three mechanisms which lead to the formation of an AGW in the auroral zone are (1) Joule heating (frictional heating of the neutral gas due to a di erence in velocity between the neutrals and the ions), (2) Lorentz momentum forcing (momentum transfer between the neutral gas and the ions due to collisions, synonymous with ion drag), and (3) heating due to particle precipitation. However, the relative importance of each mechanism is less certain (Williams et al, 1988). Chimonas and Hines (1970) presented an analytical calculation of the generation of AGWs and TIDs in an ideal inviscid isothermal windless atmosphere, using a two-dimensional auroral electrojet source function that produced a pressure perturbation in the atmosphere.…”

Section: Introductionmentioning

confidence: 99%

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A study of the Joule and Lorentz inputs in the production of atmospheric gravity waves in the upper thermosphere

Moffett

Millward

1997

Ann. Geophys.

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Abstract. First results of a modelling study of atmospheric gravity waves (AGWs) are presented. A fullycoupled global thermosphere-ionosphere-plasmasphere model is used to examine the relative importance of Lorentz forcing and Joule heating in the generation of AGWs. It is found that Joule heating is the dominant component above 110 km. The e ects of the direction of the Lorentz forcing component on the subsequent propagation of the AGW are also addressed. It is found that enhancement of zonal i Â f forcing results in AGWs at F-region altitudes of similar magnitudes travelling from the region of forcing in both poleward and equatorward directions, whilst enhancement of equatorward meridional i Â f forcing results in AGWs travelling both poleward and equatorward, but with the magnitude of the poleward wave severely attenuated compared with the equatorward wave.

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Section: Model Descriptionmentioning

confidence: 94%

Section: Model Descriptionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A study of the Joule and Lorentz inputs in the production of atmospheric gravity waves in the upper thermosphere

Moffett

Millward

1997

Ann. Geophys.

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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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“…The source region was located near the westward edge of an expanding auroral bulge and could be associated with a westward traveling surge. Williams et al [1988Williams et al [ , 1993 reported measurements of auroral electrojet activity at high latitudes and gravity waves and TIDs at lower latitudes. It was found that on many occasions, the detection of periodic ionospheric disturbances traveling southward, after a suitable time delay, was associated with the onset of auroral activity.…”

Section: Introductionmentioning

confidence: 99%

Observations of solar wind directly driven auroral electrojets and gravity waves

Huang¹,

André²,

Sofko³

1998

J. Geophys. Res.

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Abstract. One of principal objectives in studies of atmospheric gravity waves is to identify their sources. It has been hypothesized for many years that variations of the interplanetary magnetic field (IMF) can result in occurrence of the auroral electrojets in the high-latitude ionosphere and the auroral electrojets can generate gravity waves, but identification of this relationship in experiments has been difficult since gravity waves are generally observed far from the source region. In this paper, we present simultaneous observations of the IMF, auroral electrojets, and gravity waves on December 7, 1994. It is found that when the IMF Bz component turned southward, auroral electrojet currents appeared after a time delay of about 9 min. The Saskatoon HF radar observed quasiperiodic gravity waves after each burst of the auroral electrojet with a time delay of about 60-70 min. The IMF southward turnings, the auroral electrojets, and the gravity waves had a recurrence period of about 40 min. These observations show clearly the cause and effect relationship between the IMF southward turnings, the auroral electrojets, and the gravity waves. Another important phenomenon observed in this event is that the quasiperiodic occurrence of the gravity wave pulses in far-field points was determined by the repetitive energy input in the source region rather than by the wave dispersion. It seems that each burst of the auroral electrojet generated a single gravity wave pulse.

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The generation and propagation of atmospheric gravity waves observed during the Worldwide Atmospheric Gravity-wave Study (WAGS)

Cited by 72 publications

References 16 publications

A study of the Joule and Lorentz inputs in the production of atmospheric gravity waves in the upper thermosphere

A study of the Joule and Lorentz inputs in the production of atmospheric gravity waves in the upper thermosphere

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

Observations of solar wind directly driven auroral electrojets and gravity waves

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