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Vol 59, No 4 (2019)
- Year: 2019
- Articles: 12
- URL: https://journals.rcsi.science/0016-7932/issue/view/9569
Article
Model of the Ionospheric Trough for Daytime Winter Conditions Based on Data from Interkosmos-19 and Champ Satellites
Abstract
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.
383-397
Substorm Activity and Orientation of the Front of a Shock Wave of an Interplanetary Magnetic Cloud
Abstract
The paper draws attention to the complex structure of the fast magnetic clouds of the solar wind, which, in addition to the actual cloud body, contain a turbulent transition layer (cloud sheath) with a large and irregular magnetic field following the shock wave. The orientation of the plane of the magnetic-cloud shock wave with respect to the interplanetary magnetic field modified by the shock wave propagating in the solar wind for 33 cases of the registration of fast magnetic clouds has been calculated. The dependence of the substorm activity in the auroral zone on the level of turbulent processes occurring in the sheath of magnetic clouds has been studied. It was taken into account that the turbulent phenomena in the sheath are largely determined by the orientation of the shock-wave plane with respect to the interplanetary magnetic field. It is shown that the level of magnetic activity in the auroral zone, which is characterized by the integral AL index, increases with a decrease in the angle between the direction normal to the shock-wave front and the vector of the interplanetary magnetic field. Thus, the most geoeffective are magnetic clouds with a quasi-parallel shock wave, and the least geoeffective are those with a quasi-perpendicular shock wave. It was concluded that the intensity of turbulent processes in the cloud sheath increases with a decrease in the magnetic field penetrating the sheath, which plays a stabilizing role for turbulent magnetohydrodynamic perturbations.
398-406
Fast Ionospheric Dynamics during a Substorm from Vertical and Oblique Sounding Data
Abstract
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.
407-417
Representation of the Third Adiabatic Invariant in Flux Form and Some Consequences of Its Conservation by Examples of Specific Axial Magnetic Systems
Abstract
The dynamics of invariant magnetic surfaces is considered with examples of axially symmetric magnetic systems. The inner trap (magnetic mirror) and the outer trap (dipole) are distinguished in a system formed by two coils with current. The dynamics of noninteracting particles moving in the plane of the magnetic equator is considered in the drift approximation for the perturbation vector satisfying the third invariant conservation condition. The results are extended to the equator of the geomagnetic trap, in which the external perturbing field is given by the ring current. It is shown that the real effect of the ring current on plasma dynamics in the bounded magnetosphere of the Earth in the approximation of constancy of the third invariant differs from conventional model calculations based on dipole representations of the geomagnetic field. In this case, it is not the magnetic flux that makes practical sense but only its change, which is equal to the difference between the final and initial fluxes calculated by the parameters of the real field. The minimum values of the energies of charged particles in the radiation belts required to satisfy the third condition of adiabatic invariant conservation are estimated for the main phase of a particular magnetic storm.
418-428
Global Dynamic Model of Critical Frequency of the Ionospheric F2 Layer
Abstract
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.
429-440
Statistical Features of the Time Series of Variations in the Critical Frequencies of the F2 Layer
Abstract
The features of a time series of variations in the critical frequencies of the ionospheric F2 layer have been studied out based on a large file of experimental data. The stationarity of the δfoF2 samples and relative variations in the critical frequency of the F2 layer with different time resolutions have been verified. Based on a statistical analysis of δfoF2 distribution curves obtained from monthly samples of data from seven stations over a three-year period, it is shown that the distribution law of the δfoF2 set is far from normal. A model with excess and asymmetry based on a Poisson random process is proposed as a means to interpret the experimental curves of probability density functions. The analysis suggests that the model based on Poisson noise is applicable for the statistical description and probability estimations of f0F2 variations with both 1-h and 5-min resolutions during heliospheric disturbances.
441-447
Assessment of the Ionization Effect During the Distribution of a Toroidal Plasma Bunch in a Diluted Atmosphere
Abstract
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
448-457
Local and Regional Ionospheric Disturbances During Meteorological Disturbances
Abstract
Observations of atmospheric and ionospheric parameters during meteorological disturbances in November–December 2010 are analyzed. It is shown that a sharp change in atmospheric parameters, in particular, an increase in the wind gust velocity at a height of 10 m, correlates stably with local decreases in the critical frequency of the ionospheric F2 layer and the total electron content, which occur over the meteorological disturbance region ~ 3 h later. The spatial dimensions of ionospheric disturbance regions are governed by the scales of the meteorological disturbance and could reach ~1000 km. It is assumed that processes of acoustic-gravity wave excitation in the lower atmosphere are intensified in conditions of meteorological storms. Their propagation into the upper atmosphere leads to a disturbance of the thermospheric state at spatial–time scales determined by the duration and spatial scales of the meteorological disturbance region. Such large-scale thermospheric disturbances influence the circulation and electrodynamical processes in the thermosphere and ionosphere.
458-466
The Electric Field in the Surface Atmosphere of the Megapolis of Moscow
Abstract
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.
467-478
Satellite Regional Magnetic Anomalies as a Reflection of the Geological and Geophysical Properties of the Lithosphere (According to Champ Data)
Abstract
The possibilities of the use of satellite data to study lithospheric magnetic anomalies in remote and poorly studied regions are analyzed. The experiment uses data from CHAMP satellite measurements of the geomagnetic field at altitudes of ~280–320 km. Maps of the magnetic field over the territories of the North Atlantic Province, the Central Asian Fold Belt, and the Rhodope mountain range (Bulgaria) are given. The possible nature of lithospheric magnetic anomalies and their connection with deep structures and active tectonic processes in the lithosphere of the studied provinces are examined. The interpretation of the obtained maps shows that the lithospheric anomalies of the geomagnetic field are associated with modern, large-scale, geological and tectonic structures of the studied areas. The results are of interest for further complex geological and geophysical studies and the construction of valid models of the evolution of the lithosphere.
479-487
Evolution of a Gas–Dust Cloud in the Upper Atmosphere: Analysis of Events October 26, 2017
Abstract
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.
488-492
Deterministic Variability of the Ionosphere on the Eve of Strong (M ≥ 6) Earthquakes in the Regions of Greece and Italy According to Long-Term Measurements Data
Abstract
Abstract—Specific features of the variation in the electron concentration in the ionosphere in front of strong (M ≥ 6) earthquakes in the most seismically active areas of Europe, Greece and Italy, are considered on the basis of long-term measurements. Vertical sounding data (variations of the critical frequency foF2) are analyzed to cover long periods of time before the GPS/GLONASS era, and variations of the vertical total electronic content are also analyzed with the advent of global navigation satellite systems receivers in the considered regions. This analysis is based on the results of previous publications that revealed features of ionospheric precursors such as self-similarity, which is expressed in the exceptional stability of electron concentration variation as dependence on the local time. Its graphic representation is called the ionospheric precursor mask. This stability, which is defined as deterministic variability, is confirmed by the multiyear measurement data presented in this work. One new result involves the regional features of the ionospheric precursor mask found for Italy, where the mask for earthquakes in central Italy (within a radius of 300 km north of Rome) and the mask for earthquakes in southern Italy (within a radius of 300 km south of Rome) differ in phase. A possible explanation of the observed regional features is proposed.
493-508