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Vol. 12 (2009 year), No. 2

Zubova Yu.V., Namgaladze A.A.
The vibrationally excited molecular nitrogen effects by numarical modelling of the ionospheric F2-layer behaviour during major magnetic storms

The GPS derived TEC disturbances before earthquakes were discovered in the last years using global and regional TEC maps, TEC measurements over individual stations as well as measurements along individual GPS satellite passes. For strong mid-latitudinal earthquakes the seismo-ionospheric anomalies look like local TEC enhancements or decreases located in the vicinity of the forthcoming earthquake epicenter. Such structures are generated in the ionosphere for several days prior to the main shock. The amplitude of plasma modification reaches the value of 30-90 % relative to the non-disturbed level. The zone of the anomaly maximum manifestation extends larger than 1500 km in latitude and 3500-4000 km in longitude. In case of strong low-latitudinal earthquakes there are effects related with the modification of the equatorial F2-region anomaly: deepening or filling of the ionospheric electron density trough over the magnetic equator. The possible physical mechanism which can cause such anomalies has been proposed. We consider that the most probable reason of the NmF2 and TEC disturbances observed before the earthquakes is the vertical drift of the F2-region ionospheric plasma under the influence of the zonal electric field of seismic origin. To check this hypothesis, the model calculations have been carried out with the use of the UAM (Upper Atmosphere Model) – the global numerical model of the Earth’s upper atmosphere. The electric potential distribution at the near-epicenter region boundary required for the electric field maintenance has been proposed. The upper atmosphere state, presumably foregone a strong earthquake, has been modeled by means of switching-on of additional sources of the electric field in the UAM electric potential equation which was solved numerically jointly with all other UAM equations (continuity, momentum and heat balance) for neutral and ionized gases. The efficiency of the proposed mechanism has been investigated by means of model calculations of the ionosphere response to the action of zonal electric field produced by seismogenic sources located at the middle and low latitudes. The results of the corresponding numerical model calculations of the electric field and its effects in the ionospheric F2-layer and plasmasphere have been presented. They have revealed a fine agreement with TEC anomalies observed before strong earthquakes at the middle and low latitudes both in spatial scales and in amplitude characteristics.

(in Russian, стр.12, fig. 14, tables. 1, ref 24, Adobe PDF, Adobe PDF 0 Kb)

Vol. 13 (2010 year), No. 4

Knyazeva M.A., Zubova Yu.V., Namgaladze A.A.
Numerical modelling of the Weddell Sea Anomaly in behaviour of the ionospheric F2-region

The morphology and mechanism of the Weddell Sea Anomaly (WSA) forming has been investigated by using the global numerical model of the Upper Atmosphere Model and empirical model of the ionosphere IRI-2001. It has been shown that both models reproduce WSA in the summer southern hemisphere in longitudinal sector 255-315?E. It has been found that the analogous WSA longitudinal variation of the electron density takes place in the summer northern hemisphere in longitudinal sector 75-135?E. It has been shown that both phenomena are caused by the non-coincidence of the geomagnetic and geodetic axes which produces the difference in vertical velocities of the ion transfer by the thermospheric wind action in the western and eastern longitudinal sectors.

(in Russian, стр.10, fig. 6, tables. 0, ref 32, Adobe PDF, Adobe PDF 0 Kb)