Model interpretation of the ionospheric F-region electron density structures observed by ground-based satellite tomography at sub-auroral and auroral latitudes in Russia in January–May 1999

Abstract

Abstract.A satellite tomographic campaign was carried out in Russia during January-May 1999. The receiver chain consisted of four sites extending from the north of Karelia to the north of the Kola Peninsula. The F-region electron density measurements were performed during the main seasons (the winter, equinox and summer), and the data contained typical levels of solar activity (F 10.7 varied from 100 to 200). The magnetic activity was quite low (K p = 2 − 3). The Upper Atmosphere Model (UAM), the theoretical model of the Earth's atmosphere, as well as two known empirical ionospheric models, IRI-95 and RIM-88, have been applied to compare with experimental data. The tomographic images were interpreted by using simulation results obtained by the models which were also compared to one another. The analysis shows the following: (a) all three models show the best agreement with the tomography data at the height 300 km (near hmF2) in comparison with the heights below and above hmF2 (200 and 400 km); (b) all three models systematically underestimate the electron density values in comparison with the tomography data at the height 200 km and overestimate them at the height 400 km; (c) for all investigated events the N e (UAM) values are closest to N e (tomo) in 399 of 1125 examined data points (36%), N e (RIM-88) values are closest to N e (tomo) in 510 cases (45%) and N e (IRI-95) values are closest to N e (tomo) in 216 cases (19%). For the only daytime events, the N e (UAM) values are closest to N e (tomo) in 274 of 624 data points (44%), whereas N e (RIM-88) daytime values are closest to N e (tomo) in 221 cases (36%) and closest to N e (IRI-95) values in 129 cases (20%). It means that for all events RIM-88 has the best agreement with the tomography measured electron densities, whereas UAM has the best agreement with the daytime tomography measured electron densities, and IRI-95 has the worst agreement for both daytime and all events; (d) simulated UAM daytime values of electron density near the F2-layer maximum agree with corresponding tomography images for all seasons forCorrespondence to: A. N. Namgaladze (namgaladze@mstu.edu.ru) the first half of 1999, covering almost the total range of the solar activity, so that no correction of the solar EUV flux (used as an input parameter in the UAM) is required; (e) a necessary correction of simulated precipitating soft electron flux intensities has to be made, in order to improve the consistency between measured night-time values of the electron density and those estimated by the theoretical model; (f) the simulated electron density behaviour caused by spatial, diurnal, seasonal variations, as well as due to a solar activity is consistent with the experimental tomographic images. This indicates a good reliability of both experimental and simulated data (at least in the central part of the examined latitudinal interval).

The equatorward wall of the subauroral trough in the afternoon/evening sector

“…Especially the output of global numerical simulation studies should be compared to the mean properties of a trough (e.g. Sojka et al, 1985Sojka et al, , 1990Fuller-Rowell et al, 1991;Kolesnik et al, 2001;Aladjev et al, 2001;Namgaladze et al, 2003;Pryse et al, 2005; and references therein).…”

“…New analysis techniques like radiotomography have also contributed to the renewed interest in this field (e.g. Kersley et al, 1997;Aladjev et al, 2001;Namgaladze et al, 2003;Pryse et al, 1998Pryse et al, , 2005Meggs et al, 2005;Voiculescu et al, 2006; and references therein). Here we use Dynamics Explorer-2 satellite data to investigate one specific aspect of a subauroral trough, namely its equatorward wall.…”

The Global Numerical Model of the Earth’s Upper Atmosphere

“…The UAM successfully showed its ability to reproduce the general behavior of ionospheric and thermospheric parameters such as at low and high geomagnetic and solar activity conditions. A good agreement of the numerical simulations' results was achieved in comparison with observations by incoherent scatter radars located at various latitudes and longitudes (ISRs) [31], digital ionosonde CADI in the Voeykovo Main Geophysical Observatory [35], several chains of the ionospheric tomographical receivers [36][37][38], satellites, including CHAMP and GPS [3,4,26,30,[39][40][41][42], as well as with empirical models such as various types of IRI, MSIS, HWM [42][43][44][45][46][47], etc. and other theoretical models [42].…”

“…The main role of the thermospheric heating due to the soft electron precipitation was shown for the thermosphere substorm effects. The calculation results were presented in [25,26,30,[36][37][38][54][55][56][57][58][59] including the main ionospheric trough dynamics due to the ionosphere-magnetosphere convection and non-coincidence of the geographical and geomagnetic axes of the Earth. The physical mechanisms of the negative and positive F2-layer ionospheric storms (electron concentration decreases and increases, correspondingly) formation were described.…”