Kinematics and Physics of Celestial Bodies最新文献

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.

We study a system of equations, involving a large parameter, arising from the study of stellar pulsation for which a combination of procedures is used to approximate a fun damental solution. We present a combination of singular and non-singular perturbation methods which, aided by symbolic computation, may be of multi-disciplinary interest for the analysis as well as a astrophysics application. Example software is presented in the Wolfram Language (Mathematica version 13.2).

Statistical dependences of orbit parameters in four groups of sungrazing comets are studied. It is shown that the perihelia of comets of the Kreutz family are clustered around two planes (great circles of the celestial sphere). Numerical data on the observed bifurcation of perihelion distribution are provided. One of the planes basically coincides with the plane obtained by averaging orbit parameters Ω and i. The second plane with parameters Ω_p = 77.7° and i_p = 266.1° has an inclination of approximately 64° relative to the first plane. The distant nodes of cometary orbits relative to this plane are clustered at a distance of approximately 2 a.u. On the basis of the above, one of the authors hypothesizes that the comet group originates from the collision of a large comet with a meteoroid stream. This study examines some counterarguments expressed regarding this hypothesis. It is shown, based on a particular case, that the assumptions about the concentration of comet perihelia near one point and along two circles of the celestial sphere are quite compatible. The distribution of orbit inclinations relative to this plane is analyzed and a sharp maximum near 90° is noted. The maximum indicates that the parent body experienced lateral impacts of meteoroid bodies in all probability, which caused defragmentation of the former. New confirmations of the suggested hypothesis about the presence of another group of sungrazers have been found. It is assumed that the correlation dependence between the values of the perihelion parameters and ascending nodes of cometary orbits is of an evolutionary nature and is related to the group formation process. New relationships that concern the Meyer, Kracht, and Marsden groups are introduced. In particular, the authors have calculated the planes near which the cometary perihelia of these groups are concentrated. The example of the Meyer group illustrates the bifurcation of perihelia.

According to classical magnetohydrodynamics, the magnetic fields on the Sun are characterized by huge theoretically calculated time intervals of their ohmic dissipation due to the high inductance caused by the large size of the fields and the high gas kinetic electrical conductivity of the plasma. This is in striking contrast to the observed rapid changes in the structure of solar magnetism. To solve such a contradiction, it becomes relevant to search for new methods of studying magnetized plasma. Research efforts to consider turbulent motions in the plasma ended with the creation of macroscopic magnetohydrodynamics (MHD), within which substantial decreases in the electrical conductivity and magnetic permeability leading to a decrease in the calculated time of reconstruction of global magnetic fields are found. This study aims at calculating the coefficients of turbulent electrical conductivity and turbulent magnetic permeability of the solar plasma and analyzing changes in the spatiotemporal evolution of the global magnetism of the Sun considering these parameters. Macroscopic MHD methods are used for studying the behavior of global electromagnetic fields and hydrodynamic motions in turbulent plasma. For models of the photosphere and convection zone of the Sun, the distributions of the following parameters along the solar radius are calculated: coefficients of kinematic (ν), magnetic (ν_m), and turbulent (ν_T) viscosities; hydrodynamic (Re) and magnetic (Rm) Reynolds numbers; gas kinetic (σ) and turbulent (σ_T) electrical conductivities; and turbulent magnetic permeability μ_T. The theoretically calculated parameters have the following values: ν = 0.2–10 cm²/s; ν_m = 6 × 10⁸–8 × 10² cm²/s; ν_T = 10¹¹–10¹³ cm²/s; Re = 5 × 10¹¹–5 × 10¹³; Rm = 10⁴–10¹⁰; σ = 10¹¹–4 × 10¹⁶ CGS; σ_T = 10⁹–4 × 10¹¹ CGS; μ_T = 10^–2–4 × 10^–5. It is essential that σ_T ( ll ) σ and μ_T ( ll ) 1. Calculated turbulent magnetic diffusion D_T = c²/4πσ_Tμ_T turned out to be four to nine orders of magnitude higher than magnetic viscosity coefficient ν_m = c²/4πσ, which is responsible for the ohmic dissipation of magnetic fields. As a result, it becomes possible to theoretically explain the observed rapid reconstruction of magnetism on the Sun. We have revealed the radial inhomogeneity of turbulent viscosity ν_T and condition μ_T ( ll ) 1, which are indicative of the strong macroscopic diamagnetism of the solar plasma. In the lower part of the solar convection zone, the latter performs the role of negative magnetic buoyancy, thereby contributing to the for

The theoretical and experimental study of the geomagnetic effect of cosmic bodies remains an urgent problem. This is especially true for meter-sized meteoroids, for which the very existence of the magnetic effect remains in question. The purpose of this article is to present the results of the analysis of temporal variations of the X-, Y-, and Z-components of the geomagnetic field detected by the International Real-time Magnetic Observatory Network (INTERMAGNET) on the day of the Kyiv meteoroid fall and on reference days. The analysis of temporal variations has shown that the levels of these components on the day of the cosmic body explosion and on reference days were significantly different. The level of X-component with a 6 min delay decreased by 2…5 nT, which lasted approximately 60 min. With a delay of 25 min and a duration of 25 min, a quasi-periodic disturbance was observed with a variable period within 4…12 min and an amplitude increasing from 0.3…0.4 to 1.2…1.5 nT. The first disturbance, which had a speed of approximately 300 m/s, could have been caused by a blast wave. The second disturbance was most likely associated with the generation and oblique propagation of an atmospheric gravity wave with a speed of hundreds of meters per second. Within the ionosphere, the disturbance propagated at a speed of approximately 660 km/s by means of magnetohydrodynamic waves. The temporal variations of the Y- and Z-components on the day of the explosion fluctuated for 60 min and decreased by 5…10 nT. The mechanism of long-lasting disturbances of these components remains unknown. It is likely that it could be related to the diamagnetic effect. There are reasons to believe that meter-sized cosmic bodies can cause the detected magnetic effect.