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Vol. 17 (2014 year), No. 2

M.G. Botova, Yu.V. Romanovskaya, A.A. Namgaladze
Ionosphere variations: Comparison of model calculations and observation data

Electron density and ionospheric total electron content variations during different seasons and under low and high solar activity levels have been modeled using the global numerical Upper Atmosphere Model (UAM). The model results have been compared with the empirical IRI model values and observations data. The best agreement with empirical and observations values belongs to the UAM results for day-time hours, magnetic latitudes of В±45 and low solar activity irrespective of a season. The most divergence with empirical and observations values is demonstrated by the UAM results for high latitudes because of a deficiency of ionospheric observations in the polar caps.

(in Russian, стр.9, fig. 6, tables. 0, ref 34, Adobe PDF, Adobe PDF 0 Kb)

Vol. 17 (2014 year), No. 2

Yu.V. Romanovskaya, A.A. Namgaladze
Ionospheric earthquake precursors: Analysis of total electron content measurements before strong seismic events of the year 2005

The work presents regional maps of total electron content relative disturbances before strong seismic events of the year 2005. The maps were plotted using the Global Positioning System (GPS) data. These maps' analysis has been carried out, as a result anomalous total electron content variations which meet the criteria for ionospheric earthquake precursors have been distinguished. The characteristic features of the precursors have been determined.

(in Russian, стр.8, fig. 5, tables. 1, ref 24, Adobe PDF, Adobe PDF 0 Kb)

Vol. 17 (2014 year), No. 2

M.V. Rybakov, M.I. Karpov, A.A. Namgaladze
On response of the ionosphere over the Voeykovo station on the electric field variations

Vertical sounding of the ionosphere has been performed using the CADI ionosonde at the Voeykovo station (geographic coordinates 59.95 N 30.70 E and geomagnetic coordinates 56.32 N 117.96 E), St. Petersburg, Russia, from 1 till 28 February 2013. The hourly values of the F2-layer critical frequency measured by the CADI have been compared with the variations from the empirical models IRI-2012 and IRI-Plas (International Reference Ionosphere extended to the plasmasphere). The CADI foF2 values lie in the range between the IRI-2012 and IRI-Plas predictions. The critical frequencies have been also calculated using the global three-dimensional first principle Upper Atmosphere Model (UAM). The UAM calculated foF2 values agree well with the measured ones with exception of several hours around sunset when the ionospheric electric field and thermospheric winds have the greatest impact on the foF2. The relative role of the meridional and zonal components of the electric field vector in the foF2 diurnal behavior have been investigated. It has been shown that both components are important even though magnetic activity was not too high (Kp ? 4). The measurements and UAM calculations show that the ionosphere over the Voeykovo behaves like the subauroral ionosphere rather than midlatitude one.

(in Russian, стр.8, fig. 5, tables. 1, ref 13, Adobe PDF, Adobe PDF 0 Kb)