


Vol 58, No 1 (2018)
- Year: 2018
- Articles: 18
- URL: https://journals.rcsi.science/0016-7932/issue/view/9503
Article
Features of High-Latitude Ionospheric Irregularities Development as Revealed by Ground-Based GPS Observations, Satellite-Borne GPS Observations and Satellite In Situ Measurements over the Territory of Russia during the Geomagnetic Storm on March 17–18, 2015
Abstract
The dynamic picture of the response of the high- and mid-latitude ionosphere to the strong geomagnetic disturbances on March 17–18, 2015, has been studied with ground-based and satellite observations, mainly, by transionospheric measurements of delays of GPS (Global Positioning System) signals. The advantages of the joint use of ground-based GPS measurements and GPS measurements on board of the Swarm Low-Earth-Orbit satellite mission for monitoring of the appearance of ionospheric irregularities over the territory of Russia are shown for the first time. The results of analysis of ground-based and space-borne GPS observations, as well as satellite, in situ measurements, revealed large-scale ionospheric plasma irregularities observed over the territory of Russia in the latitude range of 50°–85° N during the main phase of the geomagnetic storm. The most intense ionospheric irregularities were detected in the auroral zone and in the region of the main ionospheric trough (MIT). It has been found that sharp changes in the phase of the carrier frequency of the navigation signal from all tracked satellites were recorded at all GPS stations located to the North from 55° MLAT. The development of a deep MIT was related to dynamic processes in the subauroral ionosphere, in particular, with electric fields of the intense subauroral polarization stream. Analysis of the electron and ion density values obtained by instruments on board of the Swarm and DMSP satellites showed that the zone of highly structured auroral ionosphere extended at least to heights of 850–900 km.



Penetration of Nonstationary Ionospheric Electric Fields into Lower Atmospheric Layers in the Global Electric Circuit Model
Abstract
The problem of the penetration of nonstationary ionospheric electric fields into the lower atmospheric layers is considered based on the model of the global electric circuit in the Earth’s atmosphere. For the equation of the electric field potential, a solution that takes into account exponential variation in the electrical conductivity with height has been obtained. Analysis of the solution made it possible to reveal three cases of the dependence of the solution on height. The first case (the case of high frequencies) corresponds to the Coulomb approximation, when the electrical conductivity of the atmosphere can be neglected. In the case of low frequencies (when the frequency of changes in the ionosphere potential is less than the quantity reciprocal to the time of electric relaxation of the atmosphere), a quasi-stationary regime, in which the variation in the electric potential of the atmosphere is determined by the electric conduction currents, occurs. In the third case, due to the increase in the electrical conductivity of the atmosphere, two spherical regions appear: with the Coulomb approximation in the lower region and conduction currents in the upper one. For these three cases, formulas for estimating the electric field strength near the Earth’s surface have been obtained.



Correlation between Long-Term Variations in the Vertical Component of the Electric Field in Baikal and Solar Activity
Abstract
The vertical component of the electric field along the surface–bottom baseline was measured for several years in the southwestern part of Baikal. The measurements revealed a correlation between long-term variations in the field that were interpreted as variations in the current in the hydrospheric segment of the global electric circuit with intermittent variations in the solar activity. However, the continuous measurement series were no longer than a year, which is shorter than the maximal quasi-period of the alternating variations. The first continuous two-year measurement series was made in 2014–2016. Its analysis shows quite strong variations with quasi-periods of up to 320 days, which correlate with variations in the solar X-ray flux. The effective delay of the correlation is about four days, which is evidence of an indirect effect of solar activity on the vertical current in the hydrosphere by rather slow atmospheric processes.



Index of the Long-Term Influence of Sporadic Solar Activity on Cosmic Ray Modulation
Abstract
Coronal mass ejections (CMEs) not only produce Forbush effects but contribute to long-term modulations of cosmic rays. That makes coronal ejections the main sporadic manifestations of the solar activity, which should be considered in modulation models. In this paper, a new version of the CME-index is proposed based on a comparison of the data from satellite coronographs with Forbush effects and long-term variations of cosmic rays.



Effects in the Geomagnetic Field and Absorption of Cosmic Radio Emission Caused by the Negative Pressure Discontinuity of the Solar Wind: Analysis of a Particular Event
Abstract
An abrupt decrease in the solar wind pressure and its effect on the magnetosphere and ionosphere during the event occurring on April 4, 1971, are studied. This event differs fundamentally from a typical sudden commencement (SC) of a geomagnetic storm or from a positive sudden impulse (SI+) and is determined as a negative sudden impulse (SI–). The geomagnetic variations at different latitudes and the cosmic radio emission in the auroral zone are analyzed. From the data of low-latitude geomagnetic observatories, several subsequent negative impulses observed with a periodicity of ~45 min were found. At the same time, a sudden decrease in the absorption of cosmic radio emission in the auroral zone was revealed. Possible physical explanations of the observed changes are discussed.



Parallel Electric Field and Electron Acceleration: an Advanced Model
Abstract
A kinetic theory is necessary to explain the electron flows forming strong field-aligned currents in the auroral region. Its construction in this paper is based on the following propositions. (a) In the equatorial region, the arrival of electrons through the lateral surface of the magnetic flux tube is compensated for by their escape along the magnetic field. This is provided by action of the pitch-angle diffusion mechanism in the presence of plasma turbulence concentrated in this region. (b) Outside the equatorial region, the distribution functions of trapped and precipitating particles become “frozen.” The distributions and particle concentrations are calculated there in a model with conservation of the total energy and the magnetic moment. (c) The quasi-neutrality condition yields a large-scale parallel electric field, which contributes to the conserved total energy. In this field, the electron acceleration occurs, causing strong field-aligned currents directed upward from the ionosphere.



Variations of Geomagnetic Cosmic Ray Thresholds and Their Latitudinal Behavior in the Period of Solar Disturbance in September 2005
Abstract
The period of interplanetary, geomagnetic and solar disturbances of September 7–15, 2005, is characterized by two sharp increases of solar wind velocity to 1000 km/s and great Dst variation of the geomagnetic field (~140 nT). The time variations of theoretical and experimental geomagnetic thresholds observed during this strong geomagnetic storm, their connection with solar wind parameters and the Dst index, and the features of latitudinal behavior of geomagnetic thresholds at particular times of the storm were studied. The theoretical geomagnetic thresholds were calculated with cosmic ray particle tracing in the magnetic field of the disturbed magnetosphere described by Ts01 model. The experimental geomagnetic thresholds were specified by spectrographic global survey according to the data of cosmic ray registration by the global station network.



Paleointensity Behavior and Intervals Between Geomagnetic Reversals in the Last 167 Ma
Abstract
The results of comparative analysis of the behavior of paleointensity and polarity (intervals between reversals) of the geomagnetic field for the last 167 Ma are presented. Similarities and differences in the behavior of these characteristics of the geomagnetic field are discussed. It is shown that bursts of paleointensity and long intervals between reversals occurred at high mean values of paleointensity in the Cretaceous and Paleogene. However, there are differences between the paleointensity behavior and the reversal regime: (1) the characteristic times of paleointensity variations are less than the characteristic times of the frequency of geomagnetic reversals, (2) the achievement of maximum values of paleointensity at the Cretaceous–Paleogene boundary and the termination of paleointensity bursts after the boundary of 45–40 Ma are not marked by explicit features in the geomagnetic polarity behavior.



Signatures of Alfvenic Field-Line Resonance in the Behavior of Preonset Auroral Arcs
Abstract
The evolution of preonset auroral arcs before full-scale auroral poleward expansion (the time T0 indicates the expansion onset) is studied based on ground-based optical observations filtered by the gradient method. In one of the three events studied in detail, the preonset arc exhibits periodic poleward excursions ~10 min before T0. The excursions extend over 1° in latitude, being repeated with a period of 2.5 min (frequency 6.7 mHz), and can be explained by the theory of classical (i.e., linear nondispersive) Alfvénic fieldline resonance (FLR), which is proposed to form and evolve at the location of subsequent substorm initiation. In two other events, the preonset arc evolves somewhat differently. Having appeared 15–20 min before T0, the arc brightens and develops a fine structure in the transverse direction, with new arcs detaching and propagating away from it. Such signatures may indicate a nonlinear dispersive FLR that periodically produces soliton-like structures propagating across and away from the resonance layer. The involved nonlinearity has a ponderomotive nature. The dispersive effects become significant if, as a result of fine structuring, perturbations are produced on the scales of order of the electron inertial length or ion gyroradius.



Heating of Ions by Small-Scale Electric Field Inhomogeneities in the Auroral Ionosphere During Geomagnetic Disturbances
Abstract
In this paper, measurements of thermal and superthermal ions on the Interball-2 satellite are compared with the results of numerical simulation based on geomagnetic disturbances on December 7, 1996. It is shown that kinetic processes at small scales can have a significant effect on large-scale processes in high latitudes, leading to heating and the formation of ion fluxes and also to the formation of regions with an increased plasma density. Based on the analysis, the mechanisms that should be included in the large-scale ionosphere–magnetosphere models for the adequate description of the ion outflow from the ionosphere to the magnetosphere are determined.



Winter Anomaly in the Critical Frequency of the E-Layer in the Nighttime Polar Cap
Abstract
With the medians of the E-layer critical frequency foE measured at Resolute Bay and Casey ionospheric stations located in the polar caps of the Northern and Southern Hemispheres, it is found that these medians are higher at the nighttime hours (2100–0300 LT) in the local winter than in local summer. For Resolute Bay station, which is located above the Arctic Circle, the latter means that the foE median is higher at polar night than at polar day. Thus, the effect of a winter anomaly in the foE median in the nighttime polar cap is detected. The amplitude of that anomaly (the ratio of the local winter foE values to local summer values) could reach 15–20% and 10–15% for Resolute Bay and Casey stations, respectively. It is assumed that the winter anomaly in the foE median in the nighttime polar cap is caused by the winter–summer asymmetry in the accelerated electron energy fluxes precipitating into this region.



Behavior of Parameters of Enhancements in the Nighttime Electron Concentration in the Ionospheric F2 Layer
Abstract
We have analyzed the behavior of the F2 layer parameters during nighttime periods of enhanced electron concentration by the results of vertical sounding of the ionosphere carried out with five-minute periodicity in Almaty (76°55′ E, 43°15′ N) in 2001–2012. The results are obtained within the frameworks of the unified concept of different types of ionospheric plasma disturbances manifested as variations in the height and half-thickness of the layer accompanied by an increase and decrease of NmF2 at the moments of maximum compression and expansion of the layer. A good correlation is found between height hAm, which corresponds to the maximum increase, and layer peak height hmF, while hAm is always less than hmF. The difference between hAm and hmF linearly increases with increasing hmF. Whereas the difference is ~38 km for hmF = 280 km, it is ~54 km for hmF = 380 km. Additionally, the correlation is good between the increase in the electron concentration in the layer maximum ΔNm and the maximum enhancement at the fixed height ΔN; the electron concentration enhancement in the layer maximum is about two to three times lower than its maximum enhancement at the fixed height.



Possible Short-Term Precursors of Strong Crustal Earthquakes in Japan based on Data from the Ground Stations of Vertical Ionospheric Sounding
Abstract
We have studied changes in the ionosphere prior to strong crustal earthquakes with magnitudes of М ≥ 6.5 based on the data from the ground-based stations of vertical ionospheric sounding Kokobunji, Akita, and Wakkanai for the period 1968–2004. The data are analyzed based on hourly measurements of the virtual height and frequency parameters of the sporadic E layer and critical frequency of the regular F2 layer over the course of three days prior to the earthquakes. In the studied intervals of time before all earthquakes, anomalous changes were discovered both in the frequency parameters of the Es and F2 ionospheric layers and in the virtual height of the sporadic E layer; the changes were observed on the same day at stations spaced apart by several hundred kilometers. A high degree of correlation is found between the lead-time of these ionospheric anomalies preceding the seismic impact and the magnitude of the subsequent earthquakes. It is concluded that such ionospheric disturbances can be short-term ionospheric precursors of earthquakes.



Viscosity Coefficient of the Multicomponent Neutral Atmosphere
Abstract
The viscosity coefficient of the multicomponent neutral atmosphere calculated from the general hydrodynamic expression of a multicomponent gas mixture is compared with the approximations published and proposed in this paper for this coefficient. Two new approximate expressions for the viscosity coefficient of the multicomponent atmosphere have been found. Their relative calculation errors do not exceed 3.4 and 4.8% in the altitude range of 100 to 500 km for low, moderate, and high solar activity during daytime and nigthtime geomagnetically quiet and geomagnetically disturbed conditions at low, middle, and high latitudes. These errors are significantly smaller than the maximum relative errors (11.8–15.1%) of the viscosity coefficient calculations based on the approximations used in atmospheric studies for this coefficient. The new approximate expressions for the viscosity coefficient of the multicomponent atmosphere are recommended to be used in atmospheric studies to reduce errors in calculating atmospheric parameters.



Nonequilibrium Effects in Atmospheric Perturbations Caused by Solar Radiation Flux
Abstract
The effects of atmospheric nonequilibrium in the generation of wave perturbations due to the solar radiation flux are studied. Equations of nonequilibrium thermodynamics are used to perform an assessment of the channels of solar energy transformation into the atmosphere for different altitudes. As a result of calculations of the dispersion relation for a nonequilibrium atmosphere, we consider how the flux of solar radiation changes the spectrum of natural atmospheric oscillations at different altitudes and for different solar activities. A qualitative relation between the results of wave spectra calculations and the data of ionosphere dynamics observations for different intensities of the solar radiation flux has been established.



Magnetic and Ionospheric Effects of a Meteoroid Plume
Abstract
This paper is concerned with the study of the possibility of products of a meteoroid explosion in the atmosphere (meteoroid plume) to reach ionospheric altitudes. It has been shown that, in the case of meter-sized or larger space bodies entering the atmosphere, the plume is able to reach the lower ionosphere. The plume can be one of the sources of the formation of nacreous and noctilucent clouds. The aerosols ejected by the plume to lower ionospheric altitudes can lead to the formation of dust plasma, significantly changing the electrodynamic properties of the medium. The motion of the plume with a velocity of ~1 km/s is accompanied by the generation of a ballistic shock with a radius of 1–10 km. The relative excess pressure in the shock front can cause relative disturbances in the electron content at the altitudes of D, E, and F1 layers by ~10–100%. The geomagnetic effect of the plume and ballistic shock can reach ~1–10 nT.



Spectral Structure of Temperature Variations in the Midlatitude Mesopause Region
Abstract
Long-term series of midnight temperature in the mesopause region have been obtained from spectral observations of hydroxyl airglow emission (OH(6-2) λ840 nm band) at the Tory station (52° N, 103° E) in 2008–2016 and Zvenigorod (56° N, 37° E) station in 2000–2016. On their basis, the Lomb-Scargle spectra of the variations in the period range from ~12 days to ~11 years have been determined. Estimates of the amplitudes of statistically significant temperature fluctuations are made. The dominant oscillations are the first and second harmonics of the annual variation, the amplitudes of which are 23–24 K and 4–7 K, respectively. The remaining variations, the number of which was 16 for the Tory and 22 for Zvenigorod stations, have small amplitudes (0.5–3 K). Oscillations with combinational frequencies, which arise from modulation of the annual variation harmonics, are observed in a structure of the variation spectra in addition to interannual oscillations (periods from ~2 to ~11 years) and harmonics of the annual variation (up to its tenth harmonic).



Optical Phenomena Observed upon Some Launches of Russian Rockets
Abstract
In this paper, unusual optical phenomena observed in our country and abroad upon launches of Russian rockets are discussed and interpreted: they are regarded as the aftereffects of sunlight scattering by gas-dust clouds created by rocket fuel combustion products in different modes of engine operation. The results of instrumental observations of the clouds can be used to study physical processes in the upper atmosphere.


