Kinematics and Physics of Celestial Bodies最新文献

The influence of the Earth’s rotation on the spectrum of low-frequency wave disturbances in an isothermal atmosphere is investigated. The system of equations for small linear disturbances is obtained in the “traditional” approximation and in the β-plane approximation, taking into account the frequency of rotation of the atmosphere. The found equations differ from the previously obtained ones in that the left parts of the equations depend only on time, whereas the right parts are expressed in terms of disturbed pressure. It is shown that, at zero perturbed pressure, taking into account the atmospheric rotation in the equations leads to the “splitting” of the obtained system into separate equations describing vertical and horizontal perturbations. Compact analytical solutions were obtained for both types of disturbances. It was established that vertical disturbances are realized in the form of Brunt–Väisälä waves, while horizontal are realized in the form of Rossby waves and inertial oscillations.

In this paper, we have investigated the effect of small perturbations in the Coriolis (ϕ) and centrifugal (ψ) forces in the Photogravitational magnetic binary problem including the effect of third body as variable mass. The objective of this work is to analyse the effect of ψ and other parameters (magnetic moments (λ) and radiation pressure (q)) on the existence and evolution of equilibrium points, basins of convergence (BoC), degree of unpredictability in BoC. In addition, to examine the effect of ϕ and ψ (in the presence of other parameters) on the stability of equilibrium points are also one of the aspect of this work. For different values of parameters, a total number of cases of non-collinear equilibrium points are 3, 5 and 7. The effect of various parameters on the evolution of equilibrium points are explained with the help of graphs. All non-collinear equilibrium points are found to be unstable for permissible range of parameters present in this model. The change in geometry of BoC’s is also shown and explained using graphs. The effect of ψ, q and λ on the degree of unpredictability in BoC’s is examined using the method of basin entropy. It is found that for the complete range of λ and q, the BoC’s are in fractal region. Also, for the values of ψ = 1.37, 1.38 and 1.40 to 1.44, the boundaries of BoC’s are in non-fractal region.

An actual problem today is the search for observed evidence of the existence of deep small-scale magnetic fields of the Sun. In this regard, the authors analyzed the theoretical criterion for separating the contributions to the solar surface magnetism of two qualitatively different mechanisms of a small-scale dynamo, the action of which is hidden in the depths of the solar convection zone (SCZ), proposed by Sokoloff and Khlystova [Astron. Nachr. 2010. 331. P. 82–87]. The first mechanism ensures the generation of small-scale magnetic fields due to the interaction of turbulent motions with the mean magnetic field (small-scale dynamo-1 of macroscopic MHD), while the second mechanism causes self-excitation of magnetic fluctuations due to turbulent pulsations of highly conductive plasma ( diffusive small-scale dynamo-2 of classical MHD). The essence of the proposed criterion is that deep small-scale magnetic fields can lead under certain conditions to violations of Hale’s and Joy’s laws of observed magnetism on the surface of the Sun. Statistical analysis of these disturbances allows one to identify the differences in the evolution of the observed manifestations of two sources of small-scale fields since the contribution of two deep dynamo mechanisms to surface magnetism varies with the phase of the solar cycle in different ways. Such an important feature is the behavior of the percentage of anti-Hail groups of sunspots (in relation to the total number of sunspots) during the cycles. In the case of small-scale dynamo-1, the percentage of anti-Hale groups is independent of cycle phase, whereas the percentage of anti-Hale groups associated with diffusive small-scale dynamo-2 should reach its maximum value at solar minima. Therefore, the variations of magnetic anomalies make it possible to separate the meager contributions of two small-scale dynamo mechanisms to surface magnetism. In this connection, the task of identifying the markers of a small-scale dynamo in the solar depths from observations becomes relevant. With this in mind, we conducted an analysis of literature data of statistical studies of long series of observed violations of Hale’s and Joy’s laws, which can be caused by the presence of deep small-scale magnetic fluctuations of various origins. In particular, it was demonstrated in the work of Sokoloff, Khlystova, and Abramenko [Mon. Notic. Roy. Astron. Soc. 2015. 451. P. 1522–1527] on the basis of processing the data of different catalogs for the period 1917–2004 that the percentage of anti-Hale groups of spots increases during the minima of solar cycles. This testifies to the operation of a diffusive small-scale turbulent dynamo-2 within the SCZ, the efficiency of which becomes noticeable near the minima of the cycles, when the global toroidal magnetic field weakens. As a result of the authors' analysis of six magnetic active regions observed near the minima of the 24th and 25th solar cycles, characteristic violations of Hale’s and Joy’

We present the results of an analysis of a homogeneous 15-year series of measurements of polarimetric standards obtained using the 2.6-m Shajn telescope of the Crimean Astrophysical Observatory Research Institute of the Ministry of Education and Science of Ukraine and an aperture polarimeter with fast full modulation. Out of the 98 standards of small and large linear polarization used, we do not recommend using 11 as standards for one reason or another.

This study is aimed at comprehensively analyzing and estimating the effects in gas dynamics, as well as mechanical and optical effects, from the Kyiv meteoroid that entered the terrestrial atmosphere and exploded over Bila Tserkva raion, Kyiv oblast (Ukraine). According to the International Meteor Organization (IMO), the apparent magnitude of the meteoroid was –18. According to our estimates, the luminous power was 215 GW with an effective duration of 2.4 ± 0.2 s, the total luminous energy was 25.2 ± 2.5 GJ, and the initial kinetic energy was 0.09 ± 0.01 kt of TNT or 375 ± 35 GJ. The initial mass of the cosmic body was estimated to be 0.89 ± 0.09 t, the volume was 0.250 ± 0.025 m³, and the size was 79 ± 3 cm. The initial velocity of the meteoroid reached 29 km/s. The inclination angle, i.e., the angle that the trajectory makes with the horizontal plane, was 32°. The explosion altitude equal to 38 km and the inclination angle equal to 32° give an estimate of 3.5 t/m³ for the material density, which is close to the rock density. The energy of the processes, the gas dynamics effects, and the mechanical and optical effects from the celestial body have been analyzed. The main release of energy associated with the deceleration of the fragments of the celestial body, which was defragmented under a dynamical pressure of approximately 2.5 MPa, took place in the region with a length of 2 km at an altitude of approximately 38 km. A quasi-continuous defragmentation is suggested to produce a mass distribution that follows a power law. The main parameters of the ballistic and explosive shock waves have been estimated. For the Mach number of 97, the radius of the ballistic shock wave is estimated to be approximately 77 m, and the fundamental period to be 0.7 s, which showed a dispersive increase from 3.7 to 11.5 s with the propagation path length increasing from 50 to 5000 km. The radii of cylindrical and spherical wavefront shock waves were approximately 0.28 and 0.34 km, and their fundamental periods were approximately 2.6 and 3.2 s, respectively. These periods increased from 9.5 to 30.0 s and from 11.1 to 35.1 s with an increase in the propagation path length from 50 to 5000 km. In the vicinity of the meteoroid’s explosion height, the relative excess pressure was a maximum. It decreased with a decrease in the altitude and increased with an increase in the altitude up to approximately 120–150 km, at which it attained values of approximately 6–7% and then further decreased down to a few percent. The absolute value of the excess pressure is estimated to be near the altitude of the explosion; subsequently it decreased with a decrease in the altitude down to 20–25 km and then increased further again. At the epicenter of the explosion, it is estimated to be approximately 94 Pa for the cylindrical wavefront and approximately 99 Pa for the spherical wavefront, which is not enough to damage objects on the ground. The excess pressure decreased

The Tonga volcano is among the five most powerful volcanoes in the world. The explosion of the Tonga volcano on January 15, 2022, was unique. It has led to disturbances in the lithosphere, World Ocean, atmosphere, ionosphere, magnetosphere, and all geophysical fields. A number of studies have been devoted to the disturbance of the Earth’s magnetic field. The transport of magnetic field disturbances by atmospheric gravity waves and tsunamis, disturbances in magnetically conjugated regions due to acoustic resonance, the effect on the equatorial electrojet, etc., have been studied. This is far from the end of the variety of magnetic effects of the Tonga volcano. This study is aimed at describing the results of the analysis of global bay disturbances in the geomagnetic field observed after the Tonga volcano explosion on January 15, 2022. The results of measuring the temporal variations in the level of the X, Y, and Z components by the INTERMAGNET world network of stations are used as initial data. The analysis of the magnetic data is preceded by an analysis of space weather conditions. A preliminary analysis of temporal variations in the level of the X-, Y-, and Z-components indicates that these variations on the reference days are smoother than on January 15, 2022. An analysis of the temporal variations in the level of the X-, Y-, and Z-components of the geomagnetic field and a statistical analysis of the disturbance parameters have shown the following. Bay disturbances of all components of the geomagnetic field are observed with a time delay that varies depending on the distance to the volcano from several tens of minutes to 100–200 min. The magnitude of the effect varies from approximately 10 to approximately 60 nT. The largest disturbances occur in the Y component. The delay time and duration of disturbances increase with an increase in the distance from the volcano, while their amplitude, on the contrary, decreases. The speed of propagation of bay disturbances is close to the speed of the blast wave. Bay disturbances are weakly expressed or completely absent on the night side of the planet. It is substantiated that bay disturbances are closely related to the occurrence of an ionospheric hole under the action of a blast wave from the volcano. The results of estimates of bay disturbances are in good agreement with the observation results.

We present the results of the study of the magnetic field in the active prominence on July 24, 1999 at 07:00 UT, using the observational material obtained on the Echelle spectrograph of the horizontal solar telescope of the Astronomical Observatory of Taras Shevchenko Kyiv National University. Our analysis is based on the study of I ± V profiles of the Hα line, which were related to heights in the range of 11–20 Mm. It was found that the bisectors of the I ± V profiles are non-parallel to each other in majority of places of this prominence. This indicates the inhomogeneity of the magnetic field: with a uniform magnetic field, the named bisectors should be parallel. Moreover, the maximum splitting of bisectors is observed not only in the core of the line (which was found earlier by other authors), but also in its far wings, at distances of 1.5–2.5 Å from the line center. The specified maximum of splitting corresponds to magnetic field of about 3000 G, but this value should be considered only as a lower estimate of the true local magnetic fields. In particular, the second maximum of bisector splitting may indicate that the actual value of Zeeman splitting in small-scale structures with a small filling factor reaches the above value of 1.5–2.5 Å which corresponds to the field strength of almost 100 kG. From our study it follows that evidences on such extremely magnetic fields may not actually be a rare phenomenon, but a rather common one, which, however, can be recorded only under certain favorable observational conditions.

Acoustic gravity wave modes in the Earth’s thermosphere, the amplitude of which does not depend on height, are theoretically investigated. These studies are stimulated by satellite observations, according to which the amplitudes of acoustic gravity waves in the polar thermosphere do not show dependence on height in the altitude range of 250–450 km. It is shown that the propagation of acoustic gravity wave modes with the height-independent amplitude should be considered as an oscillatory process that occurs simultaneously at two natural frequencies. The dispersion equation for these waves is obtained. According to the frequency–wave vector diagnostic diagram, the dispersion dependence of waves with the constant amplitude is in the region that is prohibited for free propagation. It separates the waves propagating horizontally, in which the amplitude in the vertical direction increases from waves with the amplitude decreasing in the vertical direction. Solutions are found for the perturbed quantities in the two-frequency mode of oscillations. It is noted that the superposition of a few of such modes can lead to the emergence of complex resulting motions close to turbulent ones. It is shown that there is a selected quasi-harmonic mode with the constant amplitude, which is characterized by a fixed frequency and wavelength. It is concluded that this kind of wave mode with the height-independent amplitude of the perturbed values prevails in the observations in the Earth’s polar thermosphere.

The dissipation in the geomagnetic tail is a process that stops the cascade transfer of energy in the inertial turbulent range and transforms the energy of turbulent motions into heating. In the case of kinetic turbulence with the dominance of the thermal pressure over the magnetic field pressure, dissipation is also possible in the inertial range. This study considers an approach for obtaining the distribution of the energy-conversion rate (multiscale spectrum) of the electromagnetic field with the preliminary involvement of the multispacecraft method for calculating the current density. For the first time, a multiscale spectrum of the energy conversion rate in the tail of the Earth’s magnetosphere is obtained and analyzed. The results of measuring the magnetic and electric fields by the MMS mission spacecraft in the region of the current stratum and during high-speed plasma flows in the plasma layer during September 8, 2021 are used.

The explosive Tonga volcano is among the unique ones. Its order of magnitude is the same as Krakatoa (1883), St. Helens (1980), El Chichón (1982), and Pinatubo (1991) volcanoes. The uniqueness of the Tonga volcano lies in the fact that the products of eruption of the Tonga volcano rose to a record height of 50–58 km, whereas the height of eruption of the most powerful Krakatoa volcano reached only 40–55 km. The Tonga volcano has estimates of 3.9 × 10¹⁸ J for thermal energy, approximately 5.8 for volcanic explosive index VEI, approximately 5.5 for volcano magnitude M, and approximately 10.8 for eruption intensity I. We have estimated the explosion energy to be 16–18 Mt TNT. The problems of proving that a decrease in the total electron content (TEC), which was observed on January 15, 2022, in the ionosphere, was caused by the Tonga volcano explosion, and determining the principal parameters of the ionospheric hole are very urgent problems. This study is aimed at analyzing the parameters of the ionospheric hole created by the Tonga volcano explosion on January 15, 2022. Well-known GPS technologies are used to obtain data on time variations of the ionospheric TEC in the vertical column by measuring the pseudo-range and the integrated phase data at two frequencies along the path to each GPS satellite. The space weather conditions were favorable for observing the ionospheric effects caused by the explosion of the Tonga volcano. The calendar dates of January 13 and 17, which are used as reference days, were the least disturbed ones. The main results are as follows. It was found that the TEC on the reference days varied almost monotonically. Aperiodic and quasi-periodic variations of TEC were observed on the day of volcano eruption. Aperiodic variations are associated with a decrease in the TEC. This effect is called the ionospheric hole. It has been proven that the ionospheric hole is caused by a volcanic explosion. The delay time of the hole increases with an increase in the distance between the volcano and the observation site, while both the absolute value of the TEC and the relative value of its decrease are reduced. According to estimates, the horizontal size of the ionospheric hole did not exceed 10 Mm, and the time delay of its appearance did not exceed 122 min. The vertical speed of disturbance propagation was 36–72 m/s, and the horizontal speed was 2.2 km/s. The lifetime of the ionospheric hole was 120–200 min. The TEC in the ionospheric hole was reduced by approximately 2.5–10 TECU, which is a function of the distance from the volcano to the observation site, and the relative decrease ranged from –17 to –34%.