Kinematics and Physics of Celestial Bodies最新文献

The parameters of geophysical fields and numerous parameters of the Earth–atmosphere–ionosphere–magnetosphere system significantly change during a solar eclipse (SE). In particular, the planet surface temperature decreases, the convection and turbulent processes slow down, and the air temperature near the ground reduces. The inhomogeneous structure of the surface air layer notably changes, and the role of temperature fluctuations in this layer and, consequently, the role of fluctuations in the air refractive index shrink. The purposes of this work are to analyze the observations of solar limb quivering during the two last partial SE that took place near the city of Kharkiv on March 20, 2015, and June 10, 2021, and the estimates of the statistical parameters governing air convection. The SE effects in the surface air layer were observed with the optical AFR-2 chromospheric-photospheric telescope at the V.N. Karazin Kharkiv National University Astronomical Observatory 70 km to southeast of Kharkiv. The quivering of the solar limb was measured on the days of SEs (March 20, 2015, and June 10, 2021) and on the reference days in order to determine the basic parameters of the atmospheric convection. The variations in the convection parameters are qualitatively similar to variations in illumination of the Earth’s surface and in the air temperature in the surface air layer. In the summertime, all convection parameters are a factor of ~2 higher than in the springtime. The SE effect on atmospheric convection was considerably weaker on June 10, 2021, than on March 20, 2015, because of insignificant magnitude of the former SE (0.11 vs. 0.54) and the clouds which screened the solar disk, which appreciably suppressed atmospheric convection. The comparative study of convection during seven SEs in 1999–2021 has shown that the magnitude of the effect strongly depends on the season, local time, cloud thickness, the tropospheric weather, and the magnitude of a solar eclipse.

A statistical analysis of selected parameters of solar activity and orbital motion of artificial Earth satellites (AES’s) during solar cycle 24 is carried out. Inactive satellites, launch vehicle (LV) stages, and their debris moving mainly in low orbits are studied. Different analysis algorithms are applied to the time series of the solar radio flux F_10.7 and the calculated deceleration rate dP/dt of the investigated space objects (SOs): their annual statistical indices are estimated, these parameters are studied for periodicity (wavelet analysis), and a test additive decomposition into trend and seasonal components is performed. It is found that the satellite deceleration rate in the vicinity of the solar maximum (2012–2014) increases by a factor of ten. For the solar radio flux F_10.7 and the kinematic parameter dP/dt of SOs 06073 and 31117, seasonal changes, cyclicity with a period of 27 days, etc. are confirmed. A clear anticorrelation between the trends of the corresponding parameters within –0.73…‒0.95 for SO 31117 during 2011–2018 and –0.82…–0.95 for SO 37794 during 2012–2018 is observed.

The purpose of this paper is to obtain refined altitude–time dependences of radiation intensity and mass of the Chelyabinsk meteoroid during the fall, determine the size of the bolide, and build a model of destruction with an estimate of the fragment distribution parameters by mass. The study into the impact of large celestial bodies on the environment is an urgent task for forecasting environmental consequences. The radiation intensity was calculated using the time dependence of the bolide’s brightness and E. Epic’s empirical formula. The Stefan–Boltzmann law and M. Planck’s formula were used for the radiation model of a perfect black body in a limited range of wavelengths. A method was found to determine the size of the bolide according to published observations from the video recorder. For the construction of the model of continuous fragmentation, an adapted equation of individual fragments' motion was used. Three types of mass distribution of fragments were tested: logarithmically normal, power-law, and uniform. As a result of the numerical simulation, the contribution of radiation energy was determined. It was shown that 21% of the kinetic energy of a meteoroid was spent on radiation. The variations in the mass, altitude–time dependences of the bolide size, and the parameters for different distributions of fragments by mass were calculated. The diameter of the bolide head reached 2 km, and the length of the tail was 3.5–4 km. It was found that the results of fragmentation are described at the initial stage of motion by the power-law distribution, while the distribution is lognormal in denser layers of the atmosphere. The characteristics of the swarm of stone fragments that may have followed the meteoroid were estimated. The length of the swarm reached 30 km, the maximum mass of the swarm was estimated at 400 t, and the radiation energy was 0.6% relative to the initial kinetic energy of the meteoroid.

The attenuation of the acoustic-gravitational nondivergent f-mode and inelastic γ-mode in the Earth’s upper atmosphere due to viscosity and thermal conductivity is studied. To analyze the attenuation, a system of hydrodynamic equations is used, including the modified Navier–Stokes and heat transfer equations. These modified equations take into account the contribution of the background density gradient to the transfer of energy and momentum by waves. Dispersion equations are obtained for f- and γ-modes in an isothermal dissipative atmosphere. It is shown that viscosity and thermal conductivity have little effect on the frequency of these modes under typical conditions in the thermosphere. Expressions are obtained for the damping decrements of the f- and γ-modes. It was established that the decrement of the γ-mode attenuation is almost an order of magnitude higher in the Earth’s thermosphere than the corresponding decrement of the f-mode. It is also found that the attenuation of the f-mode does not depend on the thermal conductivity but is due only to the dynamic viscosity and increases with an increase in the relative contribution of the bulk viscosity. The dissipation of the γ-mode is caused by dynamic viscosity and thermal conductivity and does not depend on the bulk viscosity. The time variation of the perturbation amplitudes for the f- and γ-modes at different heights of the thermosphere is considered. The characteristic attenuation times of the f- and γ-modes at different heights depending on the wavelength, as well as at different levels of solar activity, are calculated. The boundary heights in the thermosphere above which the f-and γ-modes cannot exist due to dissipation are determined.

This article is devoted to determining Earth’s Orientation Parameters (EOP) from reprocessing of the Laser ranging observations of the specially designed satellites. These are laser geodynamics satellites Lageos and Etalon and Low Earth Orbiters Lares, Ajisai, Starlette, and Stella. New software was created by the author and a new approach was proposed to analyze each model of geodynamics phenomena; a transformation or process was first tested separately and only then included into the package. The main attention was paid to the analysis of the possibility to use Laser Ranging data to Low Earth Orbiters for EOP determination. It was shown that, despite the much lower Lares’s orbit (height is 700 km) than the Lageos’s orbit (7000 km), the resulting EOP series from Lares data have the same precision in general. It was achieved by new software and a new author approach to the study of the models. Final EOP data sets were computed at the same time by a combination of raw EOPs from each satellite or from the combination of the conditional equations. In the latter case, the precision of the final solution is 10–15% better. It allows us to recommend Low Earth orbiters for geodynamics on a permanent basis.

According to spectrophotometric measurements of Jupiter and Saturn obtained in 2014–2017 on an echelle spectrometer equipped with a CCD receiver at the Cassegrain focus of the 2-m telescope of the Nasreddin Tusi Shamakhy Astrophysical Observatory of the Azerbaijan National Academy of Sciences (ShAO), weak quadrupole lines of molecular hydrogen of the H₂ (4-0) band in the visible spectral region with a spectral resolution of R = 14 000 and R = 56 000 were studied. Using the lines of the H₂ (4-0) S(0) and S(1) bands, the pressure values at the levels of their formation, the rotational temperature, the content of molecular hydrogen in the above-cloud atmosphere, the amount of absorbing gas per the average free path of photons between two scattering acts in the cloud layer, and the specific gas content per unit free path in different parts of the disk of Jupiter and Saturn were calculated. It was necessary to monitor the change in the S₄(2)/S₄(0) ratio along the disk of Jupiter and Saturn in the spatial and temporal intervals. According to our measurements in 2016, the ratio W(0)/W(2) = 3.5 ± 0.6 for Jupiter, and W(0)/W(2) > 2.5 ± 0.4 for Saturn was obtained; in general, the Great Red Spot (GRS) has an average temperature of approximately 124 ± 6K.

An overview is given of the research work by Prof. Gustav Wilhelm Ludwig von Struve (in Russian, Lyudvig Ottovich Struve), a representative of the world-famous Struve dynasty of scholars. His work pertains to astrometry, a subfield of positional astronomy, traditionally studied by the Struves. Ludwig von Struve’s works on lunar eclipses and binary stars (in particular, the systems of η Cassiopeia and Procyon), their proper motions and positional determinations, stand out for their extraordinary methodicalness and meticulous processing. The greatest value is attached to those works by Struve where he calculates (being one the first researchers to do so) the speed of rotation of the Milky Way, refines the constant of precession, and determines the coordinates of the solar apex. At the Kharkiv Astronomical Observatory, Struve determined the positions of reference stars for the asteroid Eros, carries out long-term observations of circumpolar stars, and contributed to compiling a catalog of 779 zodiacal stars. He also organized an expedition of Kharkiv astronomers to observe the total solar eclipse of 1914. Struve’s works have been distinguished twice by the Russian Astronomical Society.

Currently, the problem of geospace storms and their components, geomagnetic storms, is one of the most important problems in solar-terrestrial physics and space geophysics. The exploration of the geospace and its use for the needs of civilization has led to the fact that our life is increasingly dependent on the manifestations of solar-terrestrial processes, the state of atmospheric-space weather, and ground-to-space systems of various purposes. The more technologically advanced our civilization becomes, the more vulnerable it is to the processes taking place on the Sun, manifestations of solar-terrestrial relationships, and variations in atmospheric-space weather. These circumstances determine the relevance and continuous scientific and practical significance of studies into the manifestations of solar-terrestrial processes and their consequences. Geospace (geomagnetic) storms can be accompanied by a number of effects: variations in the parameters of the atmosphere and geospace; deceleration of spacecraft; impact of increased cosmic radiation on crew and electronic equipment in spacecraft and aircraft; disturbances of conditions of radio wave propagation and channels of radio communication, radio navigation, radio ranging, radio position finding, radio astronomy, and remote sensing; the induction of currents in power transmission lines, cable lines, pipelines, automated railway systems; and the impact on weather- and climate-forming systems. In addition to the physical effects of individual geomagnetic storms, which are described in a large number of scientific papers, a statistical analysis of the parameters of the solar wind, interplanetary magnetic field, and geomagnetic storms over long periods is of interest. The purpose of this study is to statistically analyze the parameters of the solar wind disturbed by solar storms, the interplanetary magnetic field, and the geomagnetic activity indices over the period of solar cycle 24 (2009–2020). The main statistical characteristics of the disturbed solar wind parameters responsible for the geomagnetic storm origins (153 storms in total) over solar cycle 24 have been estimated. The main statistical characteristics of the components of the disturbed interplanetary magnetic field have been estimated, and the main statistical characteristics of the geomagnetic field indices have been obtained. With respect to magnetic activity, solar cycle 24 was quieter than solar cycle 23.

On August 4, 2020, a massive explosion rocked the city of Beirut, Lebanon. The explosion yield has been estimated to be equivalent to 1 kt of TNT, and the physical effects of the explosion on the Earth–atmosphere–ionosphere–magnetosphere system have been analyzed in detail. The possible effects of powerful explosions are of considerable interest to geophysicists and radio physicists to analyze. These effects make it possible to reveal the mechanisms for transporting the disturbances in both the vertical and horizontal directions as well as the mechanisms for interaction of the subsystems in the Earth–atmosphere–ionosphere–magnetosphere system. The purpose of the present paper is to describe radio and magnetometer observations of the processes that accompanied the powerful explosion in Beirut on August 4, 2020, in the lower ionosphere and in the geomagnetic field. The observations of the possible response of the near-Earth medium to the explosion have been made with a fluxmeter magnetometer and a radio system for sounding the ionosphere at oblique incidence. The latter system detected an increase of up to 5.3° in the phase of the ionospheric wave and an increase of 3.3% in the signal amplitude caused by an electron density change of approximately 3%. If these increases are due to the explosion, the speed of propagation of the disturbance is estimated to be approximately 3 km/s. The fluxmeter magnetometer has detected changes in the character of variations in the level of the geomagnetic field occurring 5 min and 79 min after the explosion. If these variations were associated with the explosion, the speeds of propagation can be estimated to be tens of km/s and greater as well as 490 m/s. The MHD waves have a greater speed, and the acoustic gravity waves have a smaller speed, respectively.

Observations at permanent stations of the Global Navigation Satellite System (GNSS) are directly related to global and local movements of the Earth’s crust and are also affected by various factors, such as the multipath effect and radio noise in the signal. Currently, the influence of such effects can be analyzed and excluded from further processing of GNSS observations. However, there are a number of GNSS stations that deserve more attention for the monitoring of operational stability, because they define the terrestrial implementation of the reference system. The Chernihiv station (CNIV, DOMES 15501M001), which is attributed to the class A for the definition of the European Reference Frame, is an example of such a GNSS station in the territory of Ukraine. In this article, the coordinate time series based on long continuous coordinate time series and the log file of the GNSS station Chernihiv is analyzed. The coordinates of the station during the operation of various equipment are compared, and conclusions about the stability of the station are made. It was found that the station has been working stably and has not had long interruptions in observations since its commissioning. The most significant changes that occurred at the station are associated with the change of equipment. The equipment at the station was changed three times: Trimble equipment was installed in 2005, it was replaced by NovAtel equipment in 2011, and Leica equipment was installed in 2013, which is still in operation. Analysis of the time series of this permanent station shows that there is a certain jump in the study of changes in coordinates simultaneous for all devices when the Leica equipment was installed, which is associated with the change of equipment, namely with a different system of mounting the antenna on the pole. However, in the study of coordinate residuals separately for each equipment, fluctuations in values in winter and summer are observed, which can be related to the structural deformation of the GNSS antenna.