F.S. Bessarab

Calculated and observed ionospheric parameters for a Magion 2 passage and EISCAT data on July 31, 1990

Ionospheric parameters, calculated by using a global numerically self-consistent model of the thermosphere, ionosphere, and protonosphere (GSM TIP), are compared with experimental data. For July 31, 1990, there are ground-based Common Programme 1 observations from the European Incoherent Scatter (EISCAT) radar station below about 600-km height and simultaneous satellite data obtained onboard Magion 2 of the Active mission which passed near the EISCAT station around 1540 UT at an altitude of about 2500 km. The main goal of this paper is to estimate the ability of the first-principles mathematical GSM TIP model to reproduce the real ionospheric situation in a wide altitude/latitude range. Numerical calculations were performed with the complete theoretical thermosphere-ionosphere-protonosphere model. The results presented show good agreement between the incoherent scatter radar measurements (Ne, Te, Ti, and ) and model calculations under certain model assumptions. Model runs were performed to study the influence of additional local and nonlocal heating sources, the role of vibrationally excited molecular nitrogen, and different convection patterns for the conditions under study. There is relatively good agreement between model results and experimental electron concentration data along the Magion 2 satellite orbit. It was found that the best fit results are achieved with an additional plasmaspheric heat source, while the importance of vibrationally excited molecular nitrogen has not yet been firmly established.

Model/data comparison of the F2-region parameters for the 11 August 1999 solar eclipse

Abstract The study investigated the effects of a solar eclipse on the upper atmosphere, using Global Self-Consistent Model of the Thermosphere-Ionosphere and Protonosphere (GSM-TIP) developed in West Department of IZMIRAN. We investigated the solar eclipse of August 11, 1999 with a path of totality starting at 10:00 UT over England and disappearing near the Bay of Bengal (India) at 12:34 UT. The numerical model results of the calculation of f 0 F2 were compared with experimental data of f 0 F2 obtained for the European region and collected in Ionospheric Despatch Centre in Europe (IDCE), Warsaw. The model results have shown substantial decreasing of f 0 F2 over all the European sector (of 1-1,5 MHz). The region of the depression moves from England to Turkey with maximal decreasing along eclipse path. Comparisons with experimental f 0 F2 data show a reasonable agreement for a number of station such as Warsaw, Kaliningrad, Lannion with exception of Sofia.

Model calculations of TEC over europe during 11 August 1999 solar eclipse

Abstract In this paper we presented the model calculation results of the total electron (TEC) over Europe sector obtained with using the Global Self-Consistent Model of the Thermosphere, Ionosphere and protonosphere (GSM TIP) during August 11, 1999 Solar Eclipse. The model was developed in WD of IZMIRAN and describes the three-dimensional time-dependent distribution of the upper atmosphere parameters between 80km to 15 Earths radii including electron concentration. The numerical model results of the TEC calculation have been compared with the experimental data of TEC obtained with GPS measurements on the European station located near far from the path of totality. Model results have shown substantial decreasing of TEC (25–30%) with time delay about 30 min. Comparison with experimental TEC data show a reasonable agreement for a number of station such as Hers, Graz, Lamkowko, Sofia, Ankara etc. though there are some differences in the details.

Numerical simulation of an ionospheric disturbance over EISCAT using a global ionospheric model

Abstract A global numerical model of the Earths upper atmosphere has been used to simulate numerically the behaviour of the ionosphere observed by EISCAT on 24–25 March 1987 when the quiet day of 24 March was followed by the disturbed day of 25 March, with a Sudden Commencement (SC) starting about 1540 UT. We have selected the model input data for the auroral precipitating particle fluxes and the field-aligned currents to obtain an acceptable agreement between the calculated and observed ionospheric variations. A rather good similarity between the calculated and observed variations of the electric field, E-region electron concentration, F2-region ion temperature and electron concentration has been found. Spatial distributions of the electric potential and F2-region electron concentration and ion temperature have been obtained. The dynamics of the main ionospheric trough during the disturbed period has been investigated. It has been found that the equatorward movement of the midnight part of the trough is connected with the enhanced plasma transport, while the apparent westward and eastward movements of the evening and morning edges of the trough are connected with the “hot spots” caused by Joule heating of the ion gas.

Numerical modelling of the thermosphere-ionosphere coupling during substorm

Abstract The numerical calculation results of the thermospheric parameters ( [O] [N 2 ] ratio and Tn) and critical frequencies of F2-region of ionosphere, foF2, in the global scale for the recovery phase of the substorm are presented. The calculations were executed with the use of the Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP) was constructed in the Kaliningrad Observatory of the IZMIRAN and modified in the Polar Geophysical Institute. The influences of the global distribution of Joule dissipation on the neutral atmosphere and ionosphere parameters are discussed. It is emphasised that the Joule dissipation in the neutral atmosphere is a main cause of the negative disturbance in the F2 region of the ionosphere.

Effect of the global neutral hydrogen distribution on the spatial structure and thermal balance in the upper ionosphere

Abstract A global numerical self-consistent and time-dependent model of the thermosphere, ionosphere and protonosphere (GSM TIP) was used to study the influence of atomic neutral hydrogen distribution in the exosphere on the upper ionosphere parameters for summer solstice conditions during high solar activity (F10.7 = 200). Theoretical model calculations were compared with measured ion and electron densities obtained by in situ observations along early morning and afternoon orbits of the satellite pair Active and Magion-2 on 31 July (1990). The satellites passed over Europe around 03:25 and 15:40 UT at an altitude of about 2000–2500 km during orbits 3805 and 3812. The numerical results were compared with O+, H+ Ne densities in the dawn sector and with the Ne concentration in the afternoon sector. We found that the atomic neutral hydrogen density is an essential model input parameter for upper ionosphere and plasmasphere studies. The inaccurate model input of the exospheric neutral hydrogen distribution can cause dramatic variations of the H+ density up to a factor of 2–4 and a 40% variation of the Ne concentration under the conditions of our study. On the other hand, the variability of the thermal latitudinal structure (Ti and Te) in the upper ionosphere in the altitude range from 2000 to 2500 km reaches only about 10–15%.

Influence of January 2009 stratospheric warming on HF radio wave propagation in the low-latitude ionosphere

We have considered the influence of the January 23–27, 2009 sudden stratospheric warming (SSW) event on HF radio wave propagation in the equatorial ionosphere. This event took place during extremely low solar and geomagnetic activity. We use the simulation results obtained with the Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP) for simulating environmental changes during the SSW event. We both qualitatively and quantitatively reproduced total electron content disturbances obtained from global ground network receiver observations of GPS navigation satellite signals, by setting an additional electric potential and TIME-GCM model output at a height of 80 km. In order to study the influence of this SSW event on HF radio wave propagation and attenuation, we used the numerical model of radio wave propagation based on geometrical optics approximation. It is shown that the sudden stratospheric warming leads to radio signal attenuation and deterioration of radio communication in the daytime equatorial ionosphere.

Stratospheric warming influence on HF radio wave propagation in the low-latitude ionosphere

The case of a strong sudden stratospheric warming (SSW), which took place on January 23–27, 2009 has been selected for study. This period was characterized by low solar (F 10.7 ∼ 70) and geomagnetic (K p < 3) activity. Peak warming accounted for on January 23–24. We present our investigation results of thermosphere-ionosphere response to the SSW obtained using Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP).

Testing the method of transverse displacements for calculating paths of the HF radio wave propagation in three dimensional inhomogeneous media

Propagation of the Russian Academy of Sciences (WD IZMIRAN), Kaliningrad, Russia There are two approaches for radio wave ray tracing when the endpoints of the ray are fixed. The standard approach is the shooting method where a ray is sent out in some direction and its landing point is used to modify the shooting direction and obtain the desired endpoint. However, there is no systematic, universal algorithm for refining the shooting direction. Another approach is based on direct utilization of the variational principle for the optical path (Fermats principle). The idea is to transform an arbitrary trajectory to an optimal one, while the endpoints of the trajectory are kept fixed according to the boundary conditions.

Ionospheric Effects of Geomagnetic Storms on 26–30 September 2011 in the Different Longitudinal Sectors and Their Impact on the HF Radio Wave Propagation

Ionospheric storm is associated with the chain of events and phenomena in space environment, beginning at the Sun transmitted through the magnetosphere into the thermosphere-ionosphere system. The Earths ionosphere plays a key role in the space radio communication, radiolocation, navigation, and operation of the satellite navigation systems GLONASS/GPS. In this study, the parameters of the ionosphere-plasmasphere system during geomagnetic storms on 26–30 September 2011 were calculated using Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP).