Numerical modelling of the thermospheric and ionospheric effects of magnetospheric processes in the cusp region

Namgaladze, A. A.; Volkov, M. A.

doi:10.1007/s005850050396

Cited by 5 publications

(13 citation statements)

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“…It means that the modelled situation corresponds to the case when B y changes from 0 to A9 nT and back to 0 during an hour. The quiet region 1 and 2 FACs and keV electron precipitation¯uxes are the same as in Namgaladze et al (1996b).…”

Section: The Modelmentioning

confidence: 99%

“…In our variant 1 of the simulation we have tried to reproduce all above mentioned features of this region. A physical motivation for our choice of the input parameters for this variant has been given in our previous paper (Namgaladze et al, 1996b) where this variant of the model input has been called``variant 3''. The soft electron precipitation region extends in longitude approximately from 9 to 15 MLT and in magnetic latitude from approximately 70 to 80°with the¯ux intensity maximum moving from 78 to 73°and back in accordance with the observations by Garbe et al (1993) and Sandholt et al (1994).…”

Section: The Modelmentioning

confidence: 99%

“…Thermospheric and ionospheric responses to the precipitation and ®eld-aligned current variations in the cusp have been investigated for the equinoctial conditions of 22 March, 1987 (low solar activity) by Namgaladze et al (1996b) using the global numerical model of the Earth's upper atmosphere (Namgaladze et al, 1988(Namgaladze et al, , 1996a. This three-dimensional time-dependent model describes the ionosphere, thermosphere and protonosphere of the Earth as a single system and includes the calculations of the electric ®elds both of magnetospheric and thermospheric (dynamo) origin.…”

Section: Introductionmentioning

confidence: 99%

“…The latter strongly in¯uence the meridional and, in particular, the zonal-wind disturbances via ion drag so these disturbances can reach values of about 200± 300 m/s in the afternoon sector at 75°±85°geomagnetic latitude. Now, in the present investigation we have studied mainly the seasonal e ects in the thermospheric and ionospheric responses to the soft electron precipitation and ®eld-aligned current variations, of the order of an hour in duration, in the summer and winter cusp regions simultaneously using the same model as in Namgaladze et al (1996b). It should be expected that seasonal e ects in the thermospheric and ionospheric disturbances may be rather signi®cant due to at least two factors: (1) seasonal variations in the background state of the undisturbed thermosphere and ionosphere, i.e., of the neutral, ion and electron densities and temperatures and electric conductivities (Fuller-Rowell et al, 1988;Sojka and Schunk, 1989;Kirkwood, 1996); and (2) seasonal variations of the``input'' parameters such as the precipitating particle¯uxes and ®eld-aligned current densities (Iijima and Potemra, 1976;Bythrow et al, 1982;Fujii and Iijima, 1987;Newell and Meng, 1988;LU et al, 1994LU et al, , 1995.…”

Section: Introductionmentioning

confidence: 99%

“…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 (i.e., symmetric relatively to the geomagnetic equator) and equal to those used earlier in our calculations for the equinoctial conditions (Namgaladze et al, 1996b) to investigate only the e ects related with the background state of the ionosphere and thermosphere.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: The Modelmentioning

confidence: 99%

Section: The Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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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Electron temperature enhancement beneath the magnetospheric cusp

Prölss

2006

J. Geophys. Res.

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[1] In the dayside polar region, soft electron precipitation and heat conduction cause a significant increase in the electron temperature of the upper ionosphere. Using DE-2 satellite data, the properties of this remarkable cusp signature are investigated. First, the location of the temperature enhancement is determined. It is found that this location is primarily dependent on the substorm activity. For geomagnetically quiet conditions (AE ' 0) the temperature peak is located near 79°invariant latitude. For each increase in the AE index by 100 nT it moves equatorward by about 1 degree. During strongly disturbed conditions it may be observed at a latitude as low as 61 degrees. Since the substorm activity is controlled by the Bz component of the interplanetary magnetic field, the location of the temperature peak is also dependent on this parameter. Besides the location, the magnitude of the temperature increase is of interest. This magnitude is found to be strongly dependent on altitude. Within the height range 280 to 940 km it increases by a factor of almost 5. Compared with altitude, other parameters like the dynamic pressure of the solar wind or the geomagnetic activity are only of secondary importance. To obtain mean latitudinal profiles of the cusp-related temperature enhancement, a superposed epoch type of averaging procedure is used. This way the basic latitudinal structure of this narrow feature is preserved. For an altitude of 700 km the following mean properties are derived: amplitude '1200 K; width at half this maximum value '2.5 degrees; distance between equatorward boundary and maximum of the temperature increase ' 3.5 degrees. In general, a decrease in the electron density is observed at the location of the temperature peak. Only in the uppermost ionosphere and during geomagnetically quiet conditions is the density observed to increase, on average. The results obtained in this study should prove very useful for both empirical and theoretical modeling of the dayside polar ionosphere. They may also shed some light on the reconfiguration of the magnetosphere in the cusp region during substorm activity.

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Monitoring the global-scale winter anomaly of total electron contents using GPS data

Huo

Yuan

et al. 2009

Earth Planet Sp

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The winter anomaly phenomenon of Total Electron Contents (TEC) at latitudes 15• -60• N and 15• S-60 • S is presented using GPS carrier-phase data obtained from GPS stations during 2002. The correlation between the [O/N 2 ] ratio estimated using the NRLMSISE-00 atmospheric model and the TEC winter anomaly is also investigated. The numerical results show that the TEC winter anomaly in different regions of the world tends to be dominated by different factors. In North America, the TEC winter anomaly is strongly affected by the magnetospheric processes in high latitudes and the [O/N 2 ] ratio. In the Euro-Africa and Russia-Asia regions, the TEC winter anomaly depends mainly on the [O/N 2 ] ratio at the latitude band of 30• -60• N, and the extent of the TEC winter anomaly gradually decreases from 60• N to 30• N. The extent of the TEC winter anomaly increases at the latitude band of 15• -30• N due to the influence of the meridional neutral wind and the seasonal changes of the subsolar point. However, the TEC winter anomaly was not observed in southern hemisphere in 2002. The TEC equinoctial asymmetries in the northern and southern hemisphere are also presented using GPS TEC values collected in March and September 2002.

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Numerical modelling of the thermospheric and ionospheric effects of magnetospheric processes in the cusp region

Cited by 5 publications

References 0 publications

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

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

Electron temperature enhancement beneath the magnetospheric cusp

Monitoring the global-scale winter anomaly of total electron contents using GPS data

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