Kinematics and Physics of Celestial Bodies最新文献

Magnetic field pulsations in the magnetosphere and the time of their detection and location on the Earth’s surface are analyzed. Measurements of magnetic field fluctuations from fluxgate magnetometers of the Cluster II satellites and measurements from ground-based magnetometers in the auroral oval region are used. The substorms on August 13, 2019, are examined. In particular, two substorms and flapping motions of the magnetotail current sheet are analyzed. The measurements from ground-based observatories are selected using the 3DView software, a tool for the visualization of spacecraft position with associated geomagnetic tail field lines. A continuous wavelet transform is used to identify geomagnetic pulsations, and an integrated representation in two frequency bands, 45–150 s (Pc4/Pi2) and 150–600 s (Pc5/Pi3), is considered to determine the pulsation type and estimate the observed shifts between the pulsations recorded in the Earth’s magnetotail and in the auroral oval region. Correlated Pi2 and Pc5 pulsations in the auroral region and in the magnetotail are detected. The magnitude of detected pulsations depends on the relative position of ground-based magnetometers and the projection of the field line on which the spacecraft are located. Based on the time delay between the maxima of geomagnetic pulsations at the Earth’s surface in relation to disturbances in the magnetosphere, the velocity of disturbance propagation along the magnetic field line is estimated.

A method of identification of acoustic-gravity waves (AGWs) in the atmosphere according to the satellite measurement data has been proposed. It has been shown that the polarization relations between fluctuations of the wave parameters (velocity, density, temperature, and pressure) for freely propagating waves and evanescent wave modes are considerably different, which makes it possible to identify different types of atmospheric waves in the experimental data. A diagnostic chart was plotted that can be used for determining a wave type and its direction of the vertical motion based on the phase shifts of the observed parameters. Using phase shifts between the velocity fluctuations and thermodynamic parameters of the atmosphere, not only the wave type but also its spectral characteristics can be determined. Verification of the proposed method was performed for identifying polar wave perturbations based on the measurements from the Dynamics Explorer 2 low-orbit satellite. Verification showed that the polarization relations of AGWs in the thermosphere preferably correspond to the gravitational branch of acoustic-gravity waves, which freely propagate in the direction of bottom up. This conclusion agrees with other results of the observations of AGWs in the atmosphere and the ionosphere using the ground and satellite methods. The evanescent waves were not observed at the considered orbits of the satellite.

Profiles of the Fe IX line at a wavelength of λ = 17.1 nm in the radiation spectrum of slow magneto-acoustic waves, propagating in coronal loops, are calculated under conditions of an optically thin layer and a constant density. The parameter values used in calculations of the line profiles are as follows: the amplitude of the velocity of particles’ displacements in a wave v₀ = 10 km/s, the width of the coronal loop is 2000 and 5000 km, the wavelength Λ = 20 000 km and 50 000 km, and the value of the Doppler width Δλ_d = 1 pm; the values for the angle of view and the wave phases were varied. The true value of the energy flux density is 622 erg/cm²s. The values of the energy flux density obtained in calculations strongly depend on the angle of view θ and the wave phase: they range from 0 and, when the values of θ are large, to 2000 erg/cm²s. The values of the Doppler velocities v_d and the velocities of nonthermal motions v_nt take maximal values of ~12 km/s at small angles θ and almost vanish at large angles θ. When the angle of view is small (θ < 30°), a weak blue asymmetry is noticeable. When the angle of view is large (θ > 30°), the asymmetry is almost invisible.

The solar eclipse (SE) on June 10, 2021, was annular and a member of Saros 147. The first contact occurred at 08:12:20 UT on June 10, 2021, and the fourth contact occurred at 13:11:19 UT. The maximal SE magnitude was observed from 09:49:50 to 11:33:43 UT. The annularity took place from 10:33:16 to 10:36:56 UT. The solar eclipse began over the territory of Canada. The shadow moved across Greenland (where the annularity took place), the Arctic Ocean, the North Pole, New Siberia Island, and the Russian Federation. The partial eclipse was observed in Mongolia, in a major part of China, in the northeast of the United States, in North Alaska, all over the Arctic Ocean, and in the North Atlantic, as well as over a major part of Ukraine, except for the Odessa, Nikolaev, and Kherson regions and Crimea. In this work, the observations of the thermal (temperature) effect of the SE of June 10, 2021, in the surface air layer in the city of Kharkiv are described; the thermal effects of eight SEs that occurred in the same region in 1999–2021 are compared. The observations of the effects in the surface air layer were made at Karazin National University Radiophysics Observatory, in the vicinity of Kharkiv. The air temperature, atmospheric pressure and humidity, and the wind speed and direction were measured with standard instrumentation. The temperature measurement accuracy was 0.1°C. The solar eclipse energy balance is estimated. The internal energy of gas in the surface atmosphere has been shown to decrease by ~5.3 × 10¹⁸ J due to the SE, which corresponds to an average power of 1.2 PW. The specific energy and power were 6.5 kJ/m³ and 1.4 W/m³. The variations in the air temperature of the surface atmosphere were observed during the day of the solar eclipse and on the reference days. They were analyzed along with the tropospheric weather for those days. The weather was not favorable for observations of the thermal effect of the eclipse. The atmospheric cooling occurring during the eclipse magnitude maximum is estimated; the decrease in the temperature amounted to approximately 1°C. The differences in the thermal effects during the eight SEs compared are explained by different seasons, local time, cloud structure, state of the Earth’s surface, and atmospheric convection.

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.