M.V. Klimenko

Longitudinal variation in the ionosphere-plasmasphere system at the minimum of solar and geomagnetic activity: Investigation of temporal and latitudinal dependences

We use the Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP) as the first-principles calculation of the physical system state, the quick-run ionospheric electron density model (NeQuick) as the climatology background, and the IRI-based Real-Time Assimilative Model (IRTAM) for a global view of the ionospheric weather during a quiet period of the December 2009 solstice. The model computations are compared to the COSMIC radio occultation profiles, CHAMP and GRACE in-situ densities, and GPS TEC. It is shown, that the plasma density in the ionosphere is generally larger in the American/Atlantic longitudinal sector at any local time. The high latitude density enhancements are visible in the GSM TIP output at different altitudes but are not reproduced by the NeQuick empirical model. Given that observational data confirm an existence of the high-latitude areas where ionospheric densities are elevated in the altitude range between 300 and 480 km, we conclude the NmF2 maximum in the GSM TIP output can be trusted. Indeed, such high-latitude NmF2, IEC and TEC maxima in the American longitude sector form on the proper places as shown by the GSM TIP data, COSMIC and GPS observations. According to our results, the high-latitude maximum of NmF2: 1) manifests itself only when the integration over LT or UT of the global maps for December 22, 2009 includes nighttime, i.e. supporting an argument of its close association with the Weddell Sea Anomaly, and 2) also appears in the Ne distribution at altitudes above the F2 peak.

Investigation of optical path functional for high and low ionospheric radio rays

Optimization method for point-to-point ionospheric ray tracing based on the direct variational principle for the optical path is proposed and applied to calculations of both high and low ionospheric rays. The main problems of low ray determination and possible ways for solving them are outlined.

Empirical model of the nighttime winter Ionospheric Trough in the Northern and Southern Hemispheres

The empirical median model of the shape and position of the MIT (Main Ionospheric Trough) in the Northern and Southern Hemispheres has been developed for the first time. The model is based on the topside sounding data of the Intercosmos-19 satellite (about 2000 passes in both hemispheres) and in situ electron density N e measurements onboard the low-orbiting CHAMP satellite (more then 20 000 passes) for high and low solar activity, accordingly.

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).