Browsing by Author "Klimenko, V. V."
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Item Restricted Numerical modeling of ionospheric effects in the middle‐ and low‐latitude F region during geomagnetic storm sequence of 9-14 September 2005(American Geophysical Union, 2011-05-27) Klimenko, M. V.; Klimenko, V. V.; Ratovsky, K. G.; Goncharenko, L. P.; Sahai, Y.; Fagundes, P. R.; Jesus, R. de; Abreu, A. J. de; Vesnin, A. M.This study presents the Global Self‐Consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP) numerical simulations of the 9–14 September 2005 geomagnetic storm effects in the middle‐ and low‐latitude ionosphere. Recent modifications to the GSM TIP model include adding an empirical model of high‐energy electron precipitation and introducing a high‐resolution (1 min) calculation of region 2 field‐aligned currents and a cross‐cap potential difference. These modifications resulted in better representation of such effects as penetration of the magnetospheric convection electric field to lower latitudes and the overshielding. The model also includes simulation of solar flare effects. Comparison of model results with observational data at Millstone Hill (42.6°N, 71.5°W, USA), Arecibo (18.3°N, 66.8°W, Puerto Rico), Jicamarca (11.9°S, 76.9°W, Peru), Palmas (10.2°S, 48.2°W, Brazil), and San Jose Campos (23.2°S, 45.9°W, Brazil) shows good agreement of ionospheric disturbances caused by this storm sequence. In this paper we consider in detail the formation mechanism of the additional layers in an equatorial ionosphere during geomagnetic storms. During geomagnetic storms, the nonuniform in height zonal electric field is generated at the geomagnetic equator. This electric field forms the additional layers in the F region of equatorial ionosphere.Item Restricted Stratification of the low-latitude and near-equatorial F2 layer, topside ionization ledge, and F3 layer: What we know about this? A review(Hindawi, 2012-02-06) Klimenko, M. V.; Zhao, B.; Karpachev, A. T.; Klimenko, V. V.A large number of researches have been devoted to the formation of additional layers in the F region of the equatorial ionosphere, first of which has been published in 1940s. Originally the occurrence of such layer was named “stratification of equatorial F2 layer.” The additional layer was later named as the F3 layer. The theoretical researches have shown that the F3 layer is formed by zonal component of electric field with assistance of meridional component of thermospheric wind and field-aligned plasma diffusion. The physical mechanism of the F3 layer formation is clearly formulated for the morning-noon period, although the F3 layer is also observed at other hours. This paper presents a brief review into the history of the additional layer researches, describes the current progress of these researches, and identifies the most important problems in this field of the ionospheric physics.Item Restricted The global thermospheric and ionospheric response to the 2008 minor sudden stratospheric warming event(American Geophysical Union, 2012-10-09) Korenkov, Y. N.; Klimenko, V. V.; Klimenko, M. V.; Bessarab, F. S.; Korenkova, N. A.; Ratovsky, K. G.; Chernigovskaya, M. A.; Shcherbakov, A. A.; Sahai, Y.; Fagundes, P. R.; De Jesus, R.; De Abreu, A. J.; Cóndor, P.This paper presents a study of thermospheric and ionospheric response to the 2008 minor sudden stratospheric warming (SSW) event. This period was characterized by low solar and geomagnetic activity. The study was performed using the Global Self-consistent Model of Thermosphere, Ionosphere, and Protonosphere (GSM TIP). Model results were compared with ionosonde data from Irkutsk, Kaliningrad, Sao Jose dos Campos, and Jicamarca. The SSW event was modeled by specifying the temperature and density perturbations at the lower boundary of the GSM TIP (80 km altitude). GSM TIP simulation allowed the reproduction of the lower thermosphere temperature disturbances (the occurrence of the quasi-wave 1 structure at 80–130 km altitude with a vertical scale of 40 km), the negative response of F2 region electron density and the positive response of electron temperature at 300 km during the 2008 minor SSW event. The main formation mechanism of the global ionospheric response is due to the disturbances (decrease) in the n(O)/n(N2) ratio. The change in zonal electric field is another important mechanism of the ionospheric response at low latitudes.Item Restricted Using IRI and GSM TIP model results as environment for HF radio wave propagation model during the geomagnetic storm occurred on September 26-29, 2011(Elsevier, 2015-05-16) Kotova, D. S.; Klimenko, M. V.; Klimenko, V. V.; Zakharov, V. E.; Ratovsky, K. G.; Nosikov, I. A.; Zhao, B.This paper analyses the geomagnetic storm on September 26–29, 2011. We compare the calculation results obtained using the Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP) and IRI-2012 (Bilitza et al., 2014) model with ground-based ionosonde data of stations at different latitudes and longitudes. We examined physical mechanisms responsible for the formation of ionospheric effects during the main phase of geomagnetic storm that occurred at the rising phase of the 24th solar cycle. We used numerical results obtained from IRI-2012 and GSM TIP models as propagation environment for HF signals from an equatorial transmitter during quiet and disturbed conditions. We used the model of HF radio wave propagation developed in I. Kant Baltic Federal University (BFU) that is based on the geometrical optics approximation. We compared the obtained radio paths in quiet conditions and during the main and recovery storm phases and evaluated radio wave attenuation in different media models.