Dynamics of the thermosphere at high latitudes

Straus, Joe M.

doi:10.1029/rg016i002p00183

Cited by 35 publications

(7 citation statements)

References 40 publications

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“…During the late morning, under active conditions it is even more equatorward. Since Chatanika is south of the auroral oval at these times, it is possible that this discrepancy arises because of Joule heating as described by Straus [1978] for his high activity curve.…”

Section: All the Theoretical Calculations Reach Their Equatorward Maxmentioning

confidence: 94%

The meridional thermospheric neutral wind measured by radar and optical techniques in the auroral region

Wickwar¹,

Meriwether²,

Hays³

et al. 1984

J. Geophys. Res.

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Radar observations of ion velocities in the magnetic zenith over Chatanika, Alaska, were used to determine the geomagnetic meridional component of the thermospheric neutral wind. Corrections for molecular diffusion and molecular ion contamination of the pure O + composition assumed for the ionosphere were included in the analysis. Comparison of the averaged diurnal variation of the meridional wind showed good agreement between the two measurement techniques. Good agreement was also found for several cases of simultaneous observations. The evidence suggested that differences were caused by gravity waves. The 7 years of radar meridional wind results were examined with respect to magnetic activity, solar cycle phase, and season. During the day, the meridional component is poleward with a maximum of about 65 m/s between 1400 and 1600 local time. During the night, the wind is equatorward with a maximum of about 175 m/s between 0200 and 0500 local time. This maximum occurs after local magnetic midnight, which is about 0130 local time. When the neutral wind is averaged for 24 hours, there is a large net equatorward flow. During periods of increased magnetic activity, the nighttime wind between 2300 and 0600 local time becomes stronger toward the equator. The average increase between 0200 and 0600 local time is about 100 m/s; however, on individual days it can be as large as 400 m/s. These data pertain mostly to equinox, but the few summer and winter observations in the data set differ in the manner predicted by theory. Comparison of these results with theoretical models shows good agreement at most times, but suggests possible heating poleward of Chatanika during the morning hours. Observed exospheric temperature increases support this hypothesis. Hays et al., 1984] should result in further improvements of the thermospheric global circulation model (TGCM) formulation for the physics of high latitude dynamics.There remains, however, a dearth of ground-based measurements of geomagnetic meridional and zonal thermospheric winds with good temporal resolution at high latitudes. These measurements are an important part of the experimental tests required to examine the validity of the comprehensive threedimensional TGCM model results. These ground-based observations provide information on the diurnal variation of the F region neutral wind within the auroral convection zone. These observations greatly complement the global latitudinal sampling of thermospheric winds by the DE-B satellite.The geomagnetic meridional component of the thermospheric neutral wind may be calculated from Chatanika incoherent-scatter radar observations of field-aligned ion motions. Because the Chatanika radar could observe the magnetic zenith directly, the need to correct for horizontal transport caused by E x B drifts is avoided. Observations obtained during the 10 years that the radar was operational at Chatanika resulted in the formation of a data set that may be applied to study the behavior of the thermospheric neutral wind under varying conditions....

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Section: All the Theoretical Calculations Reach Their Equatorward Maxmentioning

confidence: 94%

The meridional thermospheric neutral wind measured by radar and optical techniques in the auroral region

Wickwar¹,

Meriwether²,

Hays³

et al. 1984

J. Geophys. Res.

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“…The first direct experimental indications of high-speed thermospheric winds were provided using data from rocket chemical release experiments [e.g., Smith, 1968;Rees, 1971;Stoffregen, 1972;Meriwether et al, 1973], from ground-based Fabry-Perot interferometers [e.g., Hays and Robie, 1971;Nagy et al, 1974], and from a limited number of satellite orbits of the LOGACS (low-gravity accelerometer calibration system) instrument [DeVries, 1972;Wu et al, 1974;Straus, 1978]. This latter spaceborne instrument provided cross track winds that displayed large reversals at high latitude and wind speeds reaching ~ 1000 m/s.…”

Section: Neutral Wind Vector Measurementsmentioning

confidence: 99%

Thermosphere dynamics: Contributions from the first 5 years of the Dynamics Explorer Program

Killeen¹,

Roble²

1988

Reviews of Geophysics

138

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Instrumentation flown on the Dynamics Explorer 2 (DE 2) spacecraft enabled the dynamics of both the neutral and the ionized components of the Earth's upper atmosphere to be monitored over the lifetime of the spacecraft, from August 1981 to February 1983. The direct measurements of global thermospheric vector neutral winds and ion drifts were supplemented by observations of neutral and ionic constituent abundances and temperatures, precipitating particle fluxes and pitch angle distributions, electric and magnetic fields, and global-scale auroral luminosity distributions. Analysis of this unique and comprehensive global data base has led to advances in our understanding of the manner in which the Earth's thermosphere responds dynamically to the insertion of energy and momentum. We review the scientific progress achieved over the past 5 years through the efforts of members of the Dynamics Explorer science team and the other interested scientists who have used the DE data base to investigate the dynamical response of the thermosphere.

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“…We simply note that some evidence indicates that an earth tide correction of the order of 30% needs to be included at the ground [Hollingsworth, 1970]. Recent studies show that momentum and Joule heating sources due to magnetospheric electric fields mapped into the high-latitude thermosphere contribute negligibly to diurnal and semidiurnal variations, although these sources are important for the mean thermospheric circulation [Straus, 1978]. Consequently, we restrict our review in this section to the aforementioned tidal forcings due to insolation absorption, and to latent release in clouds.…”

Section: The Excitation Of Atmospheric Tidesmentioning

confidence: 99%

Theoretical studies of atmospheric tides

Forbes¹,

Garrett²

1979

Reviews of Geophysics

237

135

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Advances in the theory of atmospheric tides since the monograph by Chapman and Lindzen (1970) are comprehensively reviewed. Major developments include investigations of the effects of mean zonal winds and meridional temperature gradients, molecular viscosity and thermal conductivity, radiative damping, composition variations, and hydromagnetic coupling, including seasonal and solar cycle effects. Linearized inviscid and viscid equations of general applicability are documented in this review, and a number of quantitative studies of atmospheric tides are considered as simplifications or modifications of these equations. Recent calculations of thermal excitation due to insolation absorption by H2O and O3 below 80 km, UV and EUV absorption in the lower thermosphere, and latent heat release in the tropical troposphere are presented. Although no attempt is made to exhaustively review incoherent scatter, meteor radar, and satellite mass spectrometer contributions to the study of atmospheric tides, representative wind, temperature, and composition data from these sources are interpreted within the framework of the most recent quantitative models, and the current status of our understanding of atmospheric tides is assessed. Some potentially fruitful areas of future research are also presented.

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Dynamics of the thermosphere at high latitudes

Cited by 35 publications

References 40 publications

The meridional thermospheric neutral wind measured by radar and optical techniques in the auroral region

The meridional thermospheric neutral wind measured by radar and optical techniques in the auroral region

Thermosphere dynamics: Contributions from the first 5 years of the Dynamics Explorer Program

Theoretical studies of atmospheric tides

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