Kinematics and Physics of Celestial Bodies最新文献

Wave disturbances from the solar terminator in the morning and evening hours were investigated using a ground-based network of very low frequency (VLF) radio stations. The data of measurements of the amplitudes of VLF radio signals on the GQD–A118 radio path with a transmitter in Great Britain (GQD, f = 22.1 kHz) and a receiving point in France (A118) were used. Amplitudes of radio signals change as a result of the propagation of atmospheric waves at the altitudes of localization of the upper wall of the Earth-ionosphere VLF waveguide. This makes it possible to use a network of VLF radio stations to monitor wave activity in the mesosphere (lower ionosphere). Based on the analysis of experimental data, it was established that pronounced periodic fluctuations in the amplitudes of radio signals are observed in the evening and in the morning for several hours after the passage of the solar terminator. Histograms of the distribution of these fluctuation periods for several months were constructed. The predominance of periods of radio signal fluctuations of 20–25 min was revealed both in the evening and in the morning hours. For the evening terminator, this result is consistent with our previous studies. The predominance of approximately the same wave periods in the morning was established for the first time. It is assumed that the observed fluctuations are caused by the propagation of acoustic-gravity waves (AGWs) from the solar terminator. The existence of a dominant period probably indicates that these perturbations represent a fundamental wave mode moving synchronously with the solar terminator.

The study of MHD waves in coronal structures is of great importance in coronal seismology. The study of these waves makes it possible to reveal the physical structure and heating mechanism of the solar corona. It is of great interest to calculate the line profile in the emission spectrum of a magneto-sonic wave for various physical parameters, calculate the energy flux and compare them with observations. In this paper, the profiles of the FeIX λ171Å line in the emission spectrum of slow magneto-acoustic waves propagating in coronal loops are calculated for cases of an optically thin layer and the change in density. The line profiles were calculated for the following parameter values: wave velocity amplitude ({{upsilon }_{0}}) = 10 km/s, coronal loop width 2000 and 5000 km, wavelength Λ = 20 000 and 50 000 km, Doppler width Δλ_d = 0.01 Å, and at values of the angle of the line of sight and at different phases of the wave. The energy flux density is 622.5 erg/(cm² s). The calculated values of the energy flux density strongly depend on the angle of the line of sight and on the phase of the wave and range from zero at large values of θ to ~4 × 10³ erg/(cm² s), the values of Doppler velocities ({{upsilon }_{{text{d}}}}) and velocities of non-thermal movements ({{upsilon }_{{{text{nt}}}}}) at small values of θ have a maximum value of ~13 km/s and decrease almost to zero at large values of θ. At different values of the angle of the line of sight, the asymmetry is almost not noticeable. An interesting result is that the values of the calculated (observed) energy flux can be both much less and much more than the true value: from almost zero at small values of θ. These values depend not only on the angle of the line of sight, but also on the width of the coronal loop and the wavelength.

Nonlinear equations called the Stenflo equations are usually used for the analytical description of the propagation of internal gravity waves in the Earth’s upper atmosphere. Solutions in the form of dipole vortices, tripole vortices, and vortex chains are previously obtained by these equations. The Stenflo equations also describe rogue waves, breathers, and dark solitons. If disturbances cease to be small, then their profiles are usually deformed, and, presumably, they cannot be considered plane waves. This study shows that this is not always the case for internal gravity waves and that these waves can propagate as plane waves even with large amplitudes. An exact solution of the system of nonlinear Stenflo equations for internal gravity waves that contain nonlinear terms in the form of Poisson brackets is given. The solution is obtained in the form of plane waves with arbitrary amplitude. To find a solution, the original system of equations is transformed. It is split into equations for the stream and vorticity functions as well as equations for the perturbed density. To solve the obtained equations, the procedure of the successive zeroing of Poisson brackets is applied. As a result, linear equations that allow one to find the accurate analytical solutions for internal gravity waves in the form of plane waves with arbitrary amplitude are obtained. By solving these linear equations in two different ways, we have analytically found expressions for the perturbed quantities and the dispersion equation. The nonlinear equations obtained for the current, vorticity, and perturbed density functions can be used to find other nonlinear solutions. The given solutions in the form of plane waves with arbitrary amplitude may be of interest for the analysis of the propagation of internal gravity waves in the Earth’s atmosphere and the interpretation of experimental data.

A structural analysis of the time series of pole coordinate changes (version C01 IERS) for the period of 1975.0–2011.0 has been performed based on the nonlinear least squares method. Average estimates of the parameters of the main components of the pole movement—namely, Chandler, annual, and semiannual wobbles—are obtained for this period. The obtained values of periods T and amplitudes A of the main components are as follows: T = 433.49 ± 0.22 days and A = 160 ± 3 mas for the Chandler oscillations; T = 365.19 ± 0.37 days and A = 93 ± 5 mas for the annual oscillations; and T = 183.03 ± 0.34 days and A = 4 ± 2 mas for the semiannual oscillations. Changes in the pole coordinates are examined in the time series when focusing on the manifestation of Chandler oscillations. The dynamics of oscillation parameters (including amplitude, period, phase, and Q factor) is studied. Changes in the Chandler oscillation parameters show their interdependence. The correlation coefficient between phase and period variations is +0.94, and a similar relationship is observed between phase and amplitude variations with a correlation coefficient of +0.88. It is shown that the phase change precedes the changes in the amplitude and in the period. This behavior of the parameters of the Chandler wobble suggests that changes in the period and in the amplitude should be considered a consequence of the phase changes. It is revealed that an increase in the amplitude of Chandler oscillations correlates with a decrease in the attenuation decrement with a correlation coefficient of –0.98. These findings align with the statistical patterns articulated by Melchior, which are indicative of (a) inconstancy of the period of Chandler oscillations over time and (b) proportional changes between the period and the amplitude of oscillations. Thus, preference should be given to the one-component complicated model of the Chandler pole movement with a variable period for the studied period of time.

The cumulative solution for GPS weeks 935–1933 (December 7, 1997–January 28, 2017) was obtained in the GNSS Data Analysis Centre of the Main Astronomical Observatory of the National Academy of Sciences of Ukraine after adjustment of 6993 daily normal equation files received as a result of the regular processing and the second reprocessing campaign of archival observations. The ADDNEQ2 program of the Bernese GNSS Software ver. 5.2 was used. Before the adjustment, the times series of station coordinates received from the mentioned processing were analyzed to find outliers and determine sets of coordinates and velocities. For foreign EPN stations, the files prepared by the EUREF Permanent GNSS Network were used (EPN_outliers.lst and EPN_discontinuities.snx respectively). For 233 permanent GNSS stations, the 356 sets of coordinates and 256 sets of velocities that correspond them were established. According to the duration of observations, the coordinate sets were divided into three groups: (1) less than 1 year (94 sets), (2) 1–3 years (92 sets), (3) more than 3 years (166 sets). Four coordinate sets were excluded from further analysis. The IGb08 reference frame was realized by applying No-Net-Translation conditions on the coordinates of the IGS Reference Frame stations. The velocities of these stations were heavily constrained (10^–9 m/year for each components) that, in term of adjustment means, a fixing of velocities values. As result, the coordinates and velocities of the Ukrainian and the Eastern European stations in the IGb08 reference frame at epoch 2005.0 were estimated with high precision. The mean repeatabilities for components of station coordinates are 1.69, 1.40, and 3.63 mm for the north, east, and height components respectively.

The processes that lead to formation of spatial distribution of polarization parameters in the Earth’s atmosphere are studied. Among the modern development of devices for atmospheric polarimetric measurements, the prospects for creating equipment for on-ground measurements are highlighted. A method is described for determining polarization parameters at the celestial hemisphere with use of data on the on-ground polarimetric measurements. A spatial diagram of the mutual location of the main components in the light-scattering process is provided. Formulas for calculating the angle (AoLP) and degree (DoLP) of the celestial linear polarization in the case of light scattering by a purely gaseous component of the atmosphere are given. The effect of changes in the characteristics of the atmospheric aerosol on the specified celestial polarization parameters is considered. The key idea of the proposed method for controlling the reliability of on-ground polarimetric measurements consists in using the stability of the spatial distribution of the AoLP parameter in the celestial hemisphere. The algorithm for such control is described and recommendations for its practical application are provided. The use of the DoLP parameter is indicated as an opportunity only for qualitative evaluation of the data of on-ground polarimetric measurements. Examples of visualization of the spatial distribution of celestial polarization parameters in the model environment for a selected position, date, and time of observation are given.

The present work is carried out in order to analyze the data for more than 15 000 coronal mass ejections (CMEs) during solar cycle 24, spanning the period of 2009–2017. We investigated, the properties of two categories of CMEs, narrow (W ≤ 20°) and normal (W > 20°), including angular width, linear speed, acceleration and their location. Based on statistical analysis, it is found the following. (1) 45% of the CMEs found in the angular range of W ∼ 10° and 30° with peak at 15°. (2) 70% of the narrow and 60% normal CMEs speed lies in the range of 150–400 km/s. The occurrence rate of both categories of CMEs declines sharply at linear speeds > 400 km/s and 0.1% narrow while 1.95% are of normal category, having the speeds above than 1000 km/s. (3) The 99% of narrow and 82% of normal CMEs are biased towards deceleration whereas small portion of normal CMEs do move with positive acceleration. We observed a low correlation between linear speed and acceleration –0.13 and –0.24 for narrow and normal CMEs respectively. (4) The latitudinal distribution of almost all narrow and normal CMEs were observed from equatorial regions during solar minimum, while during solar maximum, the distribution becomes wider and appears at all latitudes for both catagories. Despite of the fact that, solar cycle 24 is a weaker one in terms of geoeffectivity, but we observe a greater number of CMEs than solar cycle 23 throughout the solar maximum.

Ionospheric effects of powerful seismic events are studied using total electron content (TEC) maps of the ionosphere (http://www.aiub.unibe.ch/download/CODE/) for the northern hemisphere, with the exception of the polar region, in the winter seasons of 2012–2018. It is shown that seismic ionospheric effect is a global effect superimposed by local effects above epicenters of individual earthquakes (EQs). Temporal TEC variations at the time of strong EQs at a large distance from their epicenters (global effect) consist of the two maxima: a precursor maximum and an aftershock maximum. Only a precursor maximum is usually recorded in TEC variations over the EQ epicenter (local effect), the amplitude of which at night (on average 8%) is about twice as high as that observed during day. The reduced amplitude values are observed always (locally and globally) for several days after a positive surge in TEC. The region of the maximum amplitude of the seismic ionospheric effect belongs to the middle latitudes, especially the range of 35° N–40° N latitudes, and, within this range, at longitudes near 30° W (Mid-Atlantic ridge) and 140° E–150° E (Japanese islands and adjacent waters of the Pacific Ocean). Latitudinal amplitude maxima of the seismic ionospheric effect agree well with the latitudinal maxima of the number of EQs in both geographic and geomagnetic coordinate systems. Changes in the number of EQs and, consequently, the ionospheric effect on geomagnetic coordinates are more organized, which is indicative of a substantial impact on seismicity of the same processes at the boundary of the liquid core and lower mantle that form the Earth’s magnetic field. In addition to seismic belts and zones of midocean ridges, an increase in TEC has been recorded along the so-called “lineaments” that mark the weakened zones of the Earth’s crust with increased flows of deep gases. The correspondence between the spatial features of seismicity and the seismic ionospheric effect gives evidence in favor of the radon mechanism of lithosphere–ionosphere coupling and indirectly confirms the role of deep gases in the formation of planetary features of seismicity.

The mechanism of electrical interaction between subsystems in the Earth–atmosphere–ionosphere–magnetosphere system is currently the least studied and substantiated subject. Moreover, some experts doubt its existence. This study is devoted to investigating the mechanisms of generation and propagation of electric fields that vary in time under the influence of transient high-energy sources of various physical nature and atmospheric turbulence enhanced by these sources, which is an urgent problem. Four options of penetration of electric fields from the atmospheric surface layer into the ionosphere have been proposed. Electrical parameters that depend on disturbances in the electric charge density and the characteristics of atmospheric turbulence have been estimated and numerically calculated for a number of high-energy sources. It is shown that the disturbances arising in the atmospheric surface layer are capable of penetrating into the ionosphere and even into the magnetosphere.