Volume 59, Nº 4 (2019)

The principles and algorithm for the construction of an empirical model of the ionospheric trough for quiet (Kр = 2) daytime (06−18 LT) winter conditions in the Northern and Southern Hemispheres are described. The model consists of models of the trough position and shape. The model of the trough position describes longitudinal variations of the trough position in terms of the geographic latitude for fixed moments of local time. The model of the trough shape describes the latitudinal–longitudinal variations of foF2 within the interval of geographic latitudes 40°−85° in both hemispheres. The model of the ionospheric trough is probabilistic, since the trough is not always observed under midday conditions. In other words, the problem consists of the construction of a model of foF2 in the daytime, high-latitude ionosphere that would describe the trough structure. Data from the Interkosmos-19 and CHAMP satellites were used to solve this problem. The IRI international model of the ionosphere was also widely used; however, according to the tests, the constructed model more adequately describes the diurnal, longitudinal, and latitudinal variations of foF2 than IRI-2016. This model, together with the previously constructed model of the nighttime trough, makes it possible to speak of the creation of a complete model of foF2 in the winter ionosphere. Soon, the complete foF2 model will be accessible at the IZMIRAN site http://www.izmiran.ru/ionosphere/sm-mit/. The model make it possible to calculate the longitudinal variations of the trough position and the latitudinal–longitudinal variations of foF2 for any local time and any level of solar activity within the range F10.7 = 70−200 for all winter months.

Synchronous studies have been conducted on the high-latitude ionosonde at Sodankyulä station and the low-latitude ionosonde in Cyprus Island, as well as on two radio paths (the Sodankyulä–Gor’kovskaya subauroral and Cyprus–Gor’kovskaya midlatitude paths) during the intense substorm of February 14, 2011. Fast processes (within 5–10 min) have been identified according to vertical sounding at Sodankyulä station: sporadic Es layers with an inclined track, multilayer tracks in Es layers, anomalous spreadF, well-expressed layers in diffuse F formations, rapid changes in the peak observed frequencies in the Es layer, and multijump Es reflections of signals. During the substorm, the sporadic Es layers and diffusion in the ionospheric F2 layer are the most stable. The data from vertical sounding at Sodankyulä station and oblique sounding on the Sodankyulä–Gor’kovskaya track have been found to agree qualitatively. The distance between Sodankyulä station and the reflection point of the Sodankyulä–Gor’kovskaya path is 400 km in the southern direction. Thus, the ionospheric processes during the substorm are qualitatively close, within 400 km. However, there is a difference between the vertical and oblique sounding data and the data from oblique sounding on the Gor’kovskaya–Cyprus track with a reflection point near the city of Chișinău.

A global dynamic model of the F2 layer of the ionosphere GDMF2 is designed to calculate foF2 in both quiet and geomagnetically disturbed conditions. The term “dynamic model” implies that the change in foF2 at middle, subauroral, and auroral latitudes depends on the current level of geomagnetic activity with consideration of the prehistory of its development. A distinctive feature of this model is the empirical approach used to create the median (background) model of foF2 for quiet geomagnetic conditions and a number of aeronomic corrections to it related to the formation of the main ionospheric trough and the auroral peak of electron density, as well as changes in the temperature and composition of the thermosphere. All of these corrections depend on the changes in the heliogeophysical conditions. The global dynamic foF2 model demonstrates considerable improvement as compared to IRI-2016 (with the option ‘STORM = ON’) by on average of ~16% at high and middle and ~7% at equatorial latitudes.

Earlier, we carried out detailed numerical studies of the initial stage of the formation and movement of a toroidal plasma bunch after its flight from a plasma gun, and we also carried out preliminary calculations of its movement in highly rarefied air, when the interaction of the plasma of a bunch and air occurs in the interpenetration mode. Based on the results, the electron concentration and the scale of the ionized region that formed during the passage of a high-speed toroidal plasma bunch through the rarefied air were estimated. When the bunch spreads at a height ∼120 km and a distance ∼50 km, the ionized area with transverse dimensions of ∼20 km has an electron concentration of ∼6 × 10⁸ cm^–3

The results of instrumental observations of the electric-field strength in the conditions of Moscow in 2014–2018 are presented and analyzed. The spectral characteristics of the electric-field variations and its daily variation are discussed. The effect of cold atmospheric fronts, hurricanes, squalls and thunderstorms, as well as technogenic phenomena (large fires), on the electric-field variation is demonstrated. It is shown that hurricanes, squalls, and thunderstorms are preceded by periods of 1 to 4 h characterized by specific electric-field variations, which can be considered a possible prognostic sign of strong atmospheric phenomena.

A sequence of digital images of a gas–dust cloud of combustion products of solid fuel that formed during the separation of rocket stages is analyzed. The images were obtained in twilight conditions from a distance of ~1500 km. The height of the cloud center reaches ~900 km, and its diameter is ~2000 km. The obtained data make it possible to estimate the dispersed composition of the cloud and the dynamic parameters of its development. The practically constant expansion velocity of the cloud, ~2 km/s, indicates that it consists of rather large, dispersed particles that do not slow down in the upper atmosphere. The proposed method can be used to clarify the physical picture of the interaction of solid-fuel combustion products with the environment.