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Vol. 1 (1998 year), No. 2

Namgaladze A.A., Martynenko O.V., Volkov M.A., Namgaladze A.N., Yurik R.Yu.
High-latitude version of the global numerical model of the Earth's upper atmosphere

The global numerical model describing the thermosphere, ionosphere and protonosphere of the Earth as a single system has been modified for the polar upper atmosphere studies. The spatial and time resolution of the model has been significantly enhanced by the use of the variable latitudinal steps of numerical integration. The model is being developed to encompass modelling of the inner part of the magnetosphere confined by the closed geomagnetic field lines and the mesosphere. The results of the model calculations for the quiet magnetic conditions have been compared with the data of the empirical ionospheric and thermospheric models as well as with the EISCAT data and, in general, reasonable agreement between theoretical and empirical data has been found. The new high-latitude version of the model has been applied as well to the investigations of the disturbed behaviour of the Earth’s upper atmosphere during geomagnetic substorms and storms and during disturbances in the cusp region. The physical mechanisms of the upper atmosphere responses to the solar wind and magnetospheric forcings have been understood by the use of the model in several case studies.

(in English, стр.62, fig. 44, tables. 0, ref 145, MS Word 95, MS Word 95 956 Kb)

Vol. 6 (2003 year), No. 1

Namgaladze A.A., Namgaladze A.N., Fadeeva Yu.V., Goncharenko L.P. and Salah J.E.
Lower thermosphere and ionosphere behaviour during a strong magnetic storm of March 31, 2001: Modelling and comparison with the Millstone Hill incoherent scatter radar measurements

The numerical global Upper Atmosphere Model (UAM) has been used for studying the lower thermosphere and ionosphere behaviour during a strong magnetic storm of March 31, 2001. A comparison of the calculation results with the Millstone Hill IS radar data obtained during this magnetic storm has been carried out. A satisfactory agreement between the measured and calculated ion temperatures, electron and ion drift velocities has been obtained. The calculated electric field variation is similar to the observed one but is twice less in magnitude. As to the neutral horizontal wind velocities, there is a large difference between the calculated values and data obtained by the Millstone Hill IS radar, down to the different signs of the wind components. This difference can be bound up to distinctions in the frequencies of the ion-neutral collisions dependent on the neutral atmosphere parameters and the ion composition, and in the electric fields measured at Millstone Hill and theoretically calculated by the UAM. The reasons of the discrepancy of the thermospheric winds simulated by the UAM and calculated at Millstone Hill have been examined. The results of this examination show that the Millstone Hill wind results are very sensitive to the measured electric field values especially when the last are so large as they were in the case, and therefore even a moderate difference between the calculated and observed electric fields may cause a significant discrepancy of the thermospheric winds simulated by the UAM and calculated at Millstone Hill.

(in English, стр.6, fig. 11, tables. 0, ref 7, MS Word 95, MS Word 95 495 Kb)

Vol. 6 (2003 year), No. 1

Shapovalova Yu.A., Namgaladze A.A. and Namgaladze A.N.
The main ionospheric trough stratification as a result of the noncoincidence of the Earth's geomagnetic and geographic axes

By the use of the global numerical upper atmosphere model (UAM) an investigation of the influence of the noncoincidence of the Earth's geomagnetic and geographic axes on the electron density distribution within the main ionospheric trough have been performed for the quiet geophysical conditions. It has been shown, that noncoincidence of the axes causes not only appreciable UT-effect, but also the main ionospheric trough stratification. This stratification appears in some longitudinal sectors due to the periodical movements of the magnetospheric convection pattern relatively to the terminator position.

(in Russian, стр.7, fig. 3, tables. 0, ref 23, MS Word 95, MS Word 95 328 Kb)