Radar and satellite measurements of an F‐region ionization enhancement in the post‐noon sector

Robinson, R. M.; Evans, David S.; Potemra, T. A.; Kelly, John

doi:10.1029/gl011i009p00899

Cited by 26 publications

(11 citation statements)

References 10 publications

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“…Based on the observations with ISIS 2 scanning photometer, Cogger et al [1] first noticed that dayside aurora had an enhancement in [14][15][16] MLT sector where happens to be the peak position of the upward region 1 field-aligned current [2] . Incoherent scattering radar observations showed that F layer electron density was frequently enhanced in this sector [3] , and the postnoon auroral "hot spot" also occurs there [4] . It is a hot topic to study the dependence of the postnoon aurora upon the interplanetary magnetic field (IMF) and the solar wind parameters.…”

Section: Introductionmentioning

confidence: 93%

Dependence of the Postnoon Auroral Intensity upon the IMF Parameters

Liu

Yang

et al. 2002

Chinese J of Geophysics

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Based on auroral observations with a multi‐channel scanning photometer at Zhongshan Station, Antarctica and interplanetary magnetic field (IMF) data obtained by WIND Satellite at the upstream of the bow shock in 1997 and 1998, the dependence of the high‐latitude postnoon auroral intensity upon the IMF components and clock angle are studied. It is shown that the 630 nm intensity depends on the IMF more directly than the 557.7nm does. The 630nm intensity decreases as the IMF Bx increasing with a correlation coefficient of ‐0.83, while the dependence of 557.7nm on IMF Bx is not so close. The auroral intensity (both 630nm and 557.7 nm) varies with the IMF By as a “V” shape, having a minimum at By=‐3 nT; while it varies with Bz as a lain “Z” shape, having two turning points at Bz=‐3 nT and Bz=2 nT respectively. The correlation coefficient between the 630nm intensity and the IMF total intensity B is 0.89, while the correlation between the 557.7nm intensity and the IMF B seems not so good. The auroral intensity varies with the IMF clock angle with an inverse “V” structure that turns at θ = 130°.

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Section: Introductionmentioning

confidence: 93%

Dependence of the Postnoon Auroral Intensity upon the IMF Parameters

Liu

Yang

et al. 2002

Chinese J of Geophysics

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“…It is this ionisation that results in the E-and F-region features, imaged by the tomographic technique, that are coincident with the auroral features observed by ground-based optical instrumentation. Robinson et al (1984), using the Sondre Stromfjord incoherent scatter radar, studied an F-region ionisation enhancement with a peak height of around 250 km associated with an upward ®eld-aligned current populated by 350 eV electrons. The density of the enhancement was around 2´10 11 m…”

Section: Discussionmentioning

confidence: 99%

“…Evans (1985) found from satellite data analysis that precipitating electrons in the energy range 0.3±3 keV carried the current out of the ionosphere in latitudinally thin structures ($20 km average width) in this local time sector. Robinson et al (1984) presented incoherent scatter measurements of an ionospheric Fregion density enhancement attributed to an upward ®eld-aligned current. They concluded that the associated electron beam located at the electric ®eld reversal, produced a region of enhanced electron density by a process similar to that established for evening sector auroral arcs, but with less energetic electrons.…”

Section: Introductionmentioning

confidence: 99%

Probing discrete auroral arcs by ionospheric tomography

Moen¹,

Berry

Kersley

et al. 1998

Ann. Geophys.

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Abstract. Optical observations of 557.7 nm and 630.0 nm emissions from discrete auroral arcs in the post-noon sector have been related to localised ®eld-aligned enhancements in the spatial distribution of E-and Flayer electron density respectively seen in images reconstructed by ionospheric tomography. Results from two case studies are presented in which meridian scanning photometer and all-sky camera observations on Svalbard have been compared to electron-density structures found by tomographic inversion of measurements made by reception of radio signals at a chain of four stations at high latitude. The F-layer features are long-lived and show exact correspondence to the red-line emissions. Transient arcs in green-line intensity result in E-region structures that are resolved in one case, but not in another where the dynamic auroral forms are separated by less than one degree of latitude. The signature of an inverted-V precipitation event is clearly evident in one example.

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“…There have been many reported ground-based and satellite investigations of the thermospheric and ionospheric responses to the soft electron precipitation and ®eld-aligned current variations in the cusp region (e.g., Shepherd, 1979;Kelly and Vickrey, 1984;Kofman and Wickwar, 1984;McCormac and Smith, 1984;Oliver et al, 1984;Robinson et al, 1984;Smith, 1984;Vennerstrom et al, 1984;Wickwar, 1984;Thayer et al, 1987;Sandholt et al, 1994;Wu et al, 1996). However, there have been no reported systematic observational pictures of the seasonal behaviour of the thermospheric and ionospheric disturbances in the cusp region, partly due to the suppressive in¯uence of the solar emission on the ionization and heating processes in the summer polar upper atmosphere.…”

Section: Introductionmentioning

confidence: 99%

Seasonal effects in the ionosphere-thermosphere response to the precipitation and field-aligned current variations in the cusp region

Namgaladze¹,

Volkov²

1998

Ann. Geophys.

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Abstract. The seasonal e ects in the thermosphere and ionosphere responses to the precipitating electron¯ux and ®eld-aligned current variations, of the order of an hour in duration, in the summer and winter cusp regions have been investigated using the global numerical model of the Earth's upper atmosphere. Two variants of the calculations have been performed both for the IMF B y < 0. In the ®rst variant, the model input data for the summer and winter precipitating¯uxes and ®eld-aligned currents have been taken as geomagnetically symmetric and equal to those used earlier in the calculations for the equinoctial conditions. It has been found that both ionospheric and thermospheric disturbances are more intensive in the winter cusp region due to the lower conductivity of the winter polar cap ionosphere and correspondingly larger electric ®eld variations leading to the larger Joule heating e ects in the ion and neutral gas temperature, ion drag e ects in the thermospheric winds and ion drift e ects in the F2-region electron concentration. In the second variant, the calculations have been performed for the events of 28±29 January, 1992 when precipitations were weaker but the magnetospheric convection was stronger than in the ®rst variant. Geomagnetically asymmetric input data for the summer and winter precipitating¯uxes and ®eld-aligned currents have been taken from the patterns derived by combining data obtained from the satellite, radar and ground magnetometer observations for these events. Calculated patterns of the ionospheric convection and thermospheric circulation have been compared with observations and it has been established that calculated patterns of the ionospheric convection for both winter and summer hemispheres are in a good agreement with the observations. Calculated patterns of the thermospheric circulation are in a good agreement with the average circulation for the Southern (summer) Hemisphere obtained from DE-2 data for IMF B y < 0 but for the Northern (winter) Hemisphere there is a disagreement at high latitudes in the afternoon sector of the cusp region. At the same time, the model results for this sector agree with other DE-2 data and with the ground-based FPI data. All ionospheric and thermospheric disturbances in the second variant of the calculations are more intensive in the winter cusp region in comparison with the summer one and this seasonal di erence is larger than in the ®rst variant of the calculations, especially in the electron density and all temperature variations. The means that the seasonal e ects in the cusp region are stronger in the thermospheric and ionospheric responses to the FAC variations than to the precipitation disturbances.

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Radar and satellite measurements of an F‐region ionization enhancement in the post‐noon sector

Cited by 26 publications

References 10 publications

Dependence of the Postnoon Auroral Intensity upon the IMF Parameters

Dependence of the Postnoon Auroral Intensity upon the IMF Parameters

Probing discrete auroral arcs by ionospheric tomography

Seasonal effects in the ionosphere-thermosphere response to the precipitation and field-aligned current variations in the cusp region

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