Atmospheric gravity waves launched by auroral currents

Chimonas, G.; Hines, C. O.

doi:10.1029/gm018p0672

Cited by 115 publications

(64 citation statements)

References 18 publications

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“…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. An assumption was made that the wave frequency x is less than the Brunt-VaÈ isaÈ laÈ frequency (thus ignoring acoustic wave solutions).…”

Section: Introductionmentioning

confidence: 99%

“…An assumption was made that the wave frequency x is less than the Brunt-VaÈ isaÈ laÈ frequency (thus ignoring acoustic wave solutions). Chimonas and Hines (1970) gave an expression for the relative importance of the Joule and Lorentz terms in the production of the AGW as where g is the gravitational acceleration, r is the atmospheric scale height, f z is the vertical component of the magnetic ®eld, g v is a characteristic wave speed, r is the Cowling conductivity and j is the current density. Note that in the auroral region, the magnetic ®eld lines are e ectively vertical so f z % f. Using values of g 9X5 m s À2 Y r 10 4 mY f z 5X4 Á 10 À5 T and g v 350 ms À1 , they obtained:…”

Section: Introductionmentioning

confidence: 99%

“…Chimonas and Hines (1970) state that for an electric ®eld of % 60 mV/m, uncertainties in the value of j lead to a variation in the value of vat of 0.1 to 10.0. Brekke (1979) used height-dependent values of j and r , re-applying them to the equation of Chimonas and Hines (1970), to yield…”

Section: Introductionmentioning

confidence: 99%

“…Richmond (1978) used a combination of analytical and numerical techniques, obtaining wave-like solutions of the equations of energy, momentum and continuity in a non-isothermal atmosphere. Although the approach is similar to that of Chimonas and Hines (1970) where x is the mean electron density over the speci®ed height range. Joule heating is dominant in the upper altitude region producing waves with mean velocity $ 640 ms À1 , whereas Lorentz forcing is dominant in the lower altitude regime producing waves with a lower velocity of $ 320 ms À1 (Hunsucker, 1982).…”

Section: Introductionmentioning

confidence: 99%

“…The model of Chimonas and Hines (1970) (upon which the calculations of Brekke, 1979 andHunsucker, 1977 are based), assumes an atmosphere perturbed only in pressure. Jing and Hunsucker (1993) presented an analytical solution to take into account density, pressure and velocity perturbations, although the simpli®cations of an ideal windless isothermal atmosphere ignoring Coriolis e ects are retained.…”

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: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

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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Climatology of medium‐scale traveling ionospheric disturbances observed by the midlatitude Blackstone SuperDARN radar

et al. 2014

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Horizontal velocities ranged from 50 to 250 m s −1 with a distribution maximum between 100 and 150 m s −1 . Horizontal wavelengths ranged from 100 to 500 km with a distribution peak at 250 km, and periods between 23 and 60 min, suggesting that the MSTIDs may be consistent with thermospheric gravity waves. A local time (LT) dependence was observed such that the dominant (southeastward) population decreased in number as the day progressed until a late afternoon increase. The secondary (northwestward) population appeared only in the afternoon, possibly indicative of neutral wind effects or variability of sources. LT dependence was not observed in other parameters. Possible solar-geomagnetic and tropospheric MSTID sources were considered. The auroral electrojet (AE) index showed a correlation with MSTID statistics. Reverse ray tracing with the HINDGRATS model indicates that the dominant population has source regions over the Great Lakes and near the geomagnetic cusp, while the secondary population source region is 100 km above the Atlantic Ocean east of the Carolinas. This suggests that the dominant population may come from a region favorable to either tropospheric or geomagnetic sources, while the secondary population originates from a region favorable to secondary waves generated via lower atmospheric convection.

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Sources and characteristics of medium‐scale traveling ionospheric disturbances observed by high‐frequency radars in the North American sector

et al. 2016

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Medium‐scale traveling ionospheric disturbances (MSTIDs) are wave‐like ionospheric perturbations routinely observed by high‐frequency radars. We focus on a class of MSTIDs observed during the winter daytime at high latitudes and midlatitudes. The source of these MSTIDs remains uncertain, with the two primary candidates being space weather and lower atmospheric processes. We surveyed observations from four high‐latitude and six midlatitude Super Dual Auroral Radar Network radars in the North American sector from November to May 2012 to 2015. The MSTIDs observed have horizontal wavelengths between ∼150 and 650 km and horizontal velocities between ∼75 and 325 m s−1. In local fall and winter seasons the majority of MSTIDs propagated equatorward, with bearings ranging from ∼125° to 225° geographic azimuth. No clear correlation with space weather activity as parameterized by AE and SYM‐H could be identified. Rather, MSTID observations were found to have a strong correlation with polar vortex dynamics on two timescales. First, a seasonal timescale follows the annual development and decay of the polar vortex. Second, a shorter 2–4 week timescale again corresponds to synoptic polar vortex variability, including stratospheric warmings. Additionally, statistical analysis shows that MSTIDs are more likely during periods of strong polar vortex. Direct comparison of the MSTID observations with stratospheric zonal winds suggests that a wind filtering mechanism may be responsible for the strong correlation. Collectively, these observations suggest that polar atmospheric processes, rather than space weather activity, are primarily responsible for controlling the occurrence of high‐latitude and midlatitude winter daytime MSTIDs.

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Atmospheric gravity waves launched by auroral currents

Cited by 115 publications

References 18 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

Climatology of medium‐scale traveling ionospheric disturbances observed by the midlatitude Blackstone SuperDARN radar

Sources and characteristics of medium‐scale traveling ionospheric disturbances observed by high‐frequency radars in the North American sector

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