Abstract
Numerical calculations of the thermospheric and ionospheric parameters above EISCAT are presented for quiet geomagnetic conditions in summer. The Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP) was used. The numerical results were obtained both with a self-consistent calculation of the electric fields of magnetospheric and dynamo-action origin and with the magnetospheric electric fields only. It was found that the dynamo-electric field has some effect on the ionospheric convection pattern during quiet geomagnetic conditions. It has a marked effect mainly on the zonal neutral wind component above EISCAT (±20 m/s at 140 km altitude). We have studied the effects of various field-aligned current (FAC) distributions on thermosphere/ionosphere parameters and we show that a qualitative agreement can be obtained with region-I and -II FAC zones at 75° and 65° geomagnetic latitude, respectively. The maximum FAC intensities have been assumed at 03â21 MLT for both regions with peak values of 2.5Ã10â7 A mâ2 (region I) and 1.25Ã10â7 A mâ2 (region II). These results are in agreement with statistical potential distribution and FAC models constructed by use of EISCAT data. The lack of decreased electron density in the night-time sector as observed by the EISCAT radar was found to be due to the spatial distribution of ionospheric convection resulting from electric fields of magnetospheric origin.Key words. Electric fields and currents · Ionosphere- atmosphere interactions · Modelling and forecasting
Highlights
It is well known that the coupling of the ionosphere and magnetosphere plays an important role in the large-scaleCorrespondence to: M
These investigations show that for very quiet geomagnetic conditions the electric ®elds above the EISCAT station are small almost throughout the whole day with the exception of the evening to night-time hours from 18 to 24 LT
We can suppose that the dynamo electric ®elds could have a marked eect on the thermosphere±ionosphere parameters above EISCAT under geomagnetically quiet conditions
Summary
It is well known that the coupling of the ionosphere and magnetosphere plays an important role in the large-scaleCorrespondence to: M. The electric ®elds of magnetospheric and dynamo origin cause modi®cations of both the neutral atmosphere (temperature, density and composition) and the ionospheric parameters (electron and ion densities, electron and ion temperatures). The statistical spatial distribution of the horizontal and ®eld±aligned currents inferred from EISCAT data was presented by Fontaine and Peymirat (1996). These investigations show that for very quiet geomagnetic conditions the electric ®elds above the EISCAT station are small almost throughout the whole day with the exception of the evening to night-time hours from 18 to 24 LT. We can suppose that the dynamo electric ®elds could have a marked eect on the thermosphere±ionosphere parameters above EISCAT under geomagnetically quiet conditions
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