Kinematics and Physics of Celestial Bodies最新文献

The propagation of evanescent acoustic-gravity waves in the atmosphere with an arbitrary altitude temperature profile is investigated. The possibility of the existence of two types of evanescent wave modes in a vertically nonisothermal atmosphere is shown. The first type is the f-mode in which the dispersion does not depend on the altitude inhomogeneity of temperature and, therefore, is carried out at any altitude level of the nonisothermal atmosphere. The second type is a recently discovered (gamma )‑mode in which the dispersion depends on the altitude temperature gradient and can be fulfilled only at certain altitude intervals. The possibility of realizing the f- and (gamma )- modes in the Earth’s atmosphere is considered, taking into account the model altitude temperature profile. It is shown that these modes can exist at the heights of local temperature extremes in the atmosphere. Moreover, they are realized only in a narrow range of spectral parameters for which the conditions for a decrease in the wave energy above and below the level of their propagation are satisfied. For the f-mode, this energy condition is fulfilled at the altitudes of the local temperature minima, while that for the (gamma )-mode is at the altitudes of the local maxima. Recommendations are given regarding the possibility of observing these modes in the atmosphere of the Earth and the Sun. In the Earth’s atmosphere, the f-mode can presumably be observed near the mesopause with the characteristic wavelength ({{lambda }_{x}} approx 75,{text{km}}) and in the solar atmosphere at the heights of the chromospheres with ({{lambda }_{x}} approx 1600,{text{km}}). The period of the f‑mode propagating in the region of the temperature minimum slightly exceeds the Brent-Väisälä period at this altitude. In the Earth’s atmosphere, the (gamma )-mode can be realized in the regions of maximum temperature, for example, at the height of the stratopause with ({{lambda }_{x}} approx 100,{text{km}}) and a period slightly larger than the Brent-Väisälä period at the altitude of its propagation.

The altitude dependences of the aerosol volume-scattering coefficient have been determined for five latitudinal belts of the Northern hemisphere of Saturn, and the probable vertical structure of the aerosol component in a range of the atmospheric pressure at 0.06−10.0 bar has been constructed. For this purpose, the results of the authors' earlier analysis of the spectrophotometric measurements of the giant planet performed in 2015 for the latitudinal belts at 17° N, 33° N, 49° N, 66° N, and 80° N in the methane absorption bands at 727 nm and 619 nm were used. It has been found that aerosol is a ubiquitous component of Saturn’s atmosphere at altitude levels of the considered range, while there are no signs of purely gas interlayers. We determined the largest values of the aerosol volume-scattering coefficient, approximately ≈2 × 10⁻⁶ cm⁻¹, in the midlatitude belt at 49° N and the smallest ones, approximately ≈1 × 10⁻⁸ cm⁻¹, in the near-pole belt at 80° N. In the considered altitude range of the atmosphere, we detected four regions of the aerosol thickening (clustering), within which the aerosol volume-scattering coefficient reaches its highest values. Particles of the thickest aerosol layer in the atmosphere of Saturn were found at altitudes with a pressure of ≈0.06 bar. With immersing deeper into the atmosphere, the aerosol volume-scattering coefficient grows to the maximal values. Here, in all of the considered latitudinal belts except that at 80° N, two aerosol clusters are formed at the highest altitudes; within these clusters, the aerosol volume-scattering coefficient reaches its maximum at altitudes with a pressure of ≈0.26 and ≈0.45 bar. These clusters are separated in height by a less dense aerosol interlayer. In deeper atmospheric layers, at pressure levels between ≈0.45−2.0 bar, the aerosol volume-scattering coefficient significantly decreases. In this region of the atmosphere, in all of the considered latitudinal belts except that at 80° N, the third in succession cluster of aerosol was found. There, the maxima of the aerosol volume-scattering coefficient are located near a pressure level of ~1.0 bar. In even deeper layers, where the atmospheric pressure is approximately ≈2.0−6.0 bar, there is a fourth in succession cluster of aerosol. It is substantially extended in height, and the maxima of the aerosol volume-scattering coefficient in its upper and lower parts are located near pressure levels of 2.7 and 4.4 bar, respectively. In the model calculations, we used the following parameters of aerosol particles: the size distribution is described by a modified gamma function; the effective radius and the variance of this distribution are 1.4 μm and 0.07, respectively; and the real part of the complex refractive index is 1.44. These model characteristics of aerosols are considered as being close to the averaged parameters of particles in the real atmosphere of Saturn at the considered altitudes

The paper provides a short historical overview of sunspot observations from their discovery until the present. The review goes beyond collecting all known historical information about the study of sunspots but highlights the research of five scientists of different epochs over five centuries since the 16th. Not as much attention is deliberately given to some well-known studies and discoveries. The focus is on the utmost long-term observations of sunspots, which provide information that expands the boundaries of classical Wolf numbers or the number of sunspots groups. Sunspots have been observed since ancient times and they were documented in ancient chronicles. Active observation of sunspots began after the invention of the telescope, probably by Hans Lippershey in the early 17th century. It is documented that Thomas Harriot was the first to observe sunspots with a telescope on December 8, 1610. It is probable that Galileo Galilei and Johann Fabricius observed sunspots almost simultaneously with him in December 1610 using a telescope, independently of each other and of Harriot. The first publication about sunspots was issued by Fabricius in June 1611. We dwell on the observations of Christoph Scheiner, Christian Horrebow, Heinrich Schwabe, and Hisako Koyama. Christoph Scheiner described his long-term observations and studies of sunspots from 1611 to 1630 in his book Rosa Ursina sive Sol, which became a model for the Sun observers for many years afterwards. Christian Horrebow was the first to speculate on the regularity of sunspots, and Heinrich Schwabe was the first in 1843 to discover the periodicity (with a period of approximately 10 years) of the number of groups of sunspots. In 1852 Rudolf Wolf, analyzing all available sources, clarified that solar activity has an 11-year periodicity. He introduced the concept of the relative sunspot number and organized regular observations and publication of their results. Hisako Koyama’s 40-year observations have helped reconcile current sunspot counts with earlier ones. Wolf’s system lasted until the beginning of the 21st century. In July 2015, a new version of the relative sunspot numbers was adopted (Version 2.0). In this paper, the ratio of “new” and “old” Wolf numbers is calculated and a table of characteristics of 11‑year cycles according to Version 2.0 is proposed. Two forecasts of the maximum of solar cycle 25 are also calculated. In the case when the precursor of the maximum is the value of the relative sunspot number in the cycle minimum (correlation coefficient r = 0.557 and P < 0.001), the predicted maximum is 135.5 ± 33.8. In the second case, when the precursor is the duration of the previous cycle (r = –0.686 and P < 0.001), the predicted maximum is 179.4 ± 18.2. Both predictions indicate that solar cycle 25 will be stronger than solar cycle 24 and weaker than solar cycle 23.

Current studies dealing with the vertical structure, composition, and microphysical characteristics of the aerosol component in the atmosphere of Saturn are reviewed. When considering the methods used in the model analysis of giant planets atmospheres, the disadvantages of forcibly assigning the number of aerosol layers and their parameters that are artificially included into the model of the vertical structure of the atmosphere are pointed out. At the same time, the advantages of the effective optical depth (EOD) method are considered. This method makes it possible to determine a qualitative pattern of the altitude distribution of cloud layers in the giant planets atmospheres and to calculate a set of microphysical parameters of their aerosol component, while no particular vertical structure is preliminary assigned to the model. The EOD method is used to determine the pressure dependence of aerosol volume scattering coefficient in the upper atmosphere of Saturn from the reflectance spectra of its integral disk measured in the methane absorption bands at 619, 727, 842, 864, and 887 nm. The model assumptions, the quantitative relationships between the main atmospheric gases, and the size distribution parameters of aerosol particles are described. It has been found that aerosols with varying scattering properties are continuously present at all of the examined altitude levels in Saturn’s atmosphere. The altitudes at which the aerosol layers become densest were determined. In the atmosphere of the planet, the most powerful cloud system exhibits two maxima in the volume-scattering coefficient at levels of approximately 270 and 430 mbar and an intermediate thickening at approximately 1.0 bar. In a pressure range of 2.2−8.0 bar, there is an extended aerosol layer, where the scattering is strongest in a pressure interval of 3.8−4.8 bar depending on the methane absorption band analyzed. The significant dispersion differences, which were revealed in the composite dependence of the aerosol volume scattering coefficient, may indicate changes in the radius and/or nature of aerosol particles in the lower layers of Saturn’s atmosphere.

A description of the method for observing the occultation of stars by asteroids at the astronomical complex for observing the occultation of stars by Solar System bodies is given. The complex uses an Apogee Alta U47 CCD camera as a light detector, which operates in a time delay and integration (TDI) mode. Results of the study of the occultation phenomenon of the TYC 1280-832-1 star by the asteroid (486) Cremona on December 5, 2019, which was obtained using this complex, are described. The decrease in brightness on the photometric curve of the TYC 1280-832-1 star at the time moment that corresponds to the ephemeris occultation time within the limits of measurement errors is observed. The decrease in brightness goes beyond the 2σ error, which was determined along the entire length of the star’s track. This value exceeds the possible level of photometry errors of the star track. A possible explanation for this effect of light attenuation by a short-term grazing occultation, when the star does not completely close, is analyzed. The theoretical model of the formation of a photometric curve for this observation method taking into account diffraction phenomena and parameters of stars in the field of view has been developed to verify this statement. We showed that this can explain the magnitude and time interval of brightness attenuation. The obtained estimates of the occultation parameters for this event are as follows: the minimum fraction of the uncovered area is 48 ± 15%, which corresponds to the position of the edge of the asteroid from the star center in fractions of its radius from –0.17 to +0.21.

The satellite laser ranging method is based on measuring the transit time of a laser pulse from the transmitter to the satellite and back to the receiver. A special feature of the TPL telescope is that the laser signal is transmitted and received by the same telescope. This requires auxiliary equipment to separate these signals. In addition, this telescope is also used for visual tracking of the object, which adds complexity to the optical design. In most cases, the signals are separated mechanically using rotating mirrors. In one position, the mirrors transmit the signal to a specific channel, and they reflect the optical signal into another channel in the other position. The rotational speed of the mirrors corresponds to the frequency of the laser transmitter. Both mirrors rotate at the same frequency but with a different phase. A logic circuit built on two D-triggers and one 2-input NAND element is used as a phase detector. The paper discusses the scheme and principle of operation of the device for mirror synchronization by signals of the control computer and mirror position sensors. This device has been successfully used at the Riga-1884 laser location station of the University of Latvia.

The study of direct and reverse, positive and negative interconnections among the subsystems in the Earth (internal spheres)–atmosphere–ionosphere–magnetosphere (EAIM) system is commonly based on high-power active experiments. One of the possible experiments is an impact of large chemical explosions in EAIM system. Examples include active experiments utilizing 5 kt TNT, 1.5 kt TNT, and 2 kt TNT yield explosions. A powerful chemical explosion has been shown earlier to affect all geospheres, viz., it generates seismic waves in the lithosphere, disturbances in the electric field, electromagnetic emissions, acoustic and atmospheric gravity waves (AGWs), traveling ionospheric disturbances, and MHD waves in the near-Earth plasma. The physical effects and ecological consequences of multiple chemical explosions and accompanying fires have also been studied earlier. The main conclusion that has been drawn in these studies is that a response to such an impact can appear in all EAIM system subsystems. This paper aims to describe the principle physical effects in the atmosphere and geospace accompanying the powerful explosion in the city of Beirut on August 4, 2020. A comprehensive analysis of the main physical processes accompanying the explosion has been performed to determine the following. The Beirut explosion yield is estimated to be approximately 1 kt TNT. More than 90% of the explosion energy was transformed into the energy of the shock, while the remaining caused damage leaving a crater roughly of 40 × 10³ m³, and a 80 kt mass of the ground was ejected. The damage size and surface area have been estimated. The thermic was estimated to have ∼100 m horizontal size, ∼46 m/s speed of its ascending, and a 1.6 min time of the ascent up to the maximum altitude of approximately 4 km. At a distance of 250 km, near Cyprus, the intensity of sound was estimated to be no less than 76 dB. The shock wave traveling upwards caused significant disturbance in the atmosphere and geospace. The increase in the pressure caused by the wave is estimated to be dozens of percent in a 86–90 km altitude range. Shock wave dissipation in the 80–90 km altitude range could cause atmospheric heating by 10–20% and the generation of AGWs with δ_p ∼ 0.1 propagating to distances of thousands of kilometers from the epicenter. The secondary waves, on account of the dynamo effect, could generate periodic variations in the geomagnetic field with an amplitude of 0.1–0.3 nT.

The propagation of cosmic rays in the interplanetary medium is considered based on the kinetic Fokker–Planck equation. The analytical expression for the anisotropic part of the cosmic ray distribution function is derived in the approximation of small anisotropy. It is shown that, under isotropic scattering of energetic charged particles on interplanetary magnetic field fluctuations, the cosmic ray distribution function depends exponentially on the cosine of the angle between the particle velocity and radial direction. The expression for the cosmic ray flux density is obtained. It is shown that the value of the particle flux density is defined by the spatial distribution of the cosmic ray density and by the temporal dependence of the particle density. The cosmic ray transport equations have been derived (the hyperdiffusion equation and the telegraph equation). On the basis of these equations, the spatiotemporal distribution of solar cosmic ray intensity and the anisotropy of the particle angular distribution are investigated.

One of the mainstreams in modern X-ray astronomy is research into extragalactic X-ray sources on the basis of the data acquired at the X-ray Multi-Mirror Newton (XMM-Newton) space observatory. According to observations, X-rays coming from galaxies are mainly radiated from their central regions, i.e., active galactic nuclei and groups of X-ray sources in the galactic disks. In this paper, we consider the cross-correlation between the 4XMM-DR9 catalog and the Hyper-Linked Extragalactic Databases and Archives (HyperLeda) of galaxies. The 4XMM-DR9 catalog is a large, up-to-date catalog of observations, which contains 550 124 unique sources and covers 2.85% of the sky, while the HyperLeda database comprises 1.5 million galaxies. Our analysis resulted in a sample of more than 5000 X-ray galaxies, most of which are active galactic nuclei of low luminosity. From this sample, we selected galaxies whose the X-ray flux exceeds F = 10^–20 J/cm²s. The sources of this kind are of particular interest since it is easier to construct an informative spectrum for them. The identified and classified catalog of 1172 manually verified galaxies—the X-ray galaxy catalog named Xgal—was created. In the Xgal catalog, most galaxies have an active X-ray nucleus; Seyfert galaxies predominate among them at short distances, while quasars are prevalent at large distances. We revealed 169 galaxies that exhibit extended nuclei with a visible surface brightness distribution and 173 galaxies with more than one X-ray source. Based on the Xgal catalog, we created a catalog of elongated X-ray galaxies (the optical angular sizes of which are a > 60″) that have X-ray sources outside the nucleus. Both catalogs are freely accessible. The Xgal catalog may serve to construct the spectra of objects of a certain class in different ranges, to develop or improve the theory of their emission, and to survey bright and extended quasars. Moreover, the entire cross-sample may be used to study active galactic nuclei with low luminosity and a large-scale structure of the universe in the X-ray range.