Subjects -> ASTRONOMY (Total: 94 journals)
Showing 1 - 46 of 46 Journals sorted alphabetically
Advances in Astronomy     Open Access   (Followers: 49)
Annual Review of Astronomy and Astrophysics     Full-text available via subscription   (Followers: 50)
Annual Review of Earth and Planetary Sciences     Full-text available via subscription   (Followers: 67)
Artificial Satellites     Open Access   (Followers: 21)
Astrobiology     Hybrid Journal   (Followers: 11)
Astronomical & Astrophysical Transactions: The Journal of the Eurasian Astronomical Society     Hybrid Journal   (Followers: 7)
Astronomical Review     Open Access   (Followers: 5)
Astronomische Nachrichten     Hybrid Journal   (Followers: 4)
Astronomy & Geophysics     Hybrid Journal   (Followers: 49)
Astronomy and Astrophysics     Full-text available via subscription   (Followers: 67)
Astronomy and Computing     Hybrid Journal   (Followers: 6)
Astronomy Letters     Hybrid Journal   (Followers: 22)
Astronomy Reports     Hybrid Journal   (Followers: 22)
Astronomy Studies Development     Open Access   (Followers: 15)
Astroparticle Physics     Hybrid Journal   (Followers: 10)
Astrophysical Bulletin     Hybrid Journal   (Followers: 4)
Astrophysics     Hybrid Journal   (Followers: 35)
Astrophysics and Space Science     Hybrid Journal   (Followers: 49)
Astrophysics and Space Sciences Transactions (ASTRA)     Open Access   (Followers: 60)
Astropolitics: The International Journal of Space Politics & Policy     Hybrid Journal   (Followers: 13)
Celestial Mechanics and Dynamical Astronomy     Hybrid Journal   (Followers: 15)
Chinese Astronomy and Astrophysics     Full-text available via subscription   (Followers: 25)
Colloid Journal     Hybrid Journal   (Followers: 2)
Comptes Rendus : Physique     Open Access   (Followers: 2)
Computational Astrophysics and Cosmology     Open Access   (Followers: 6)
Earth and Planetary Science Letters     Hybrid Journal   (Followers: 142)
Earth, Moon, and Planets     Hybrid Journal   (Followers: 47)
Earth, Planets and Space     Open Access   (Followers: 77)
EAS Publications Series     Full-text available via subscription   (Followers: 8)
EPL Europhysics Letters     Partially Free   (Followers: 8)
Experimental Astronomy     Hybrid Journal   (Followers: 38)
Expert Opinion on Astronomy and Astrophysics     Open Access   (Followers: 8)
Extreme Life, Biospeology & Astrobiology - International Journal of the Bioflux Society     Full-text available via subscription   (Followers: 4)
Few-Body Systems     Hybrid Journal   (Followers: 1)
Foundations of Physics     Hybrid Journal   (Followers: 40)
Frontiers in Astronomy and Space Sciences     Open Access   (Followers: 15)
Galaxies     Open Access   (Followers: 6)
Globe, The     Full-text available via subscription   (Followers: 3)
Gravitation and Cosmology     Hybrid Journal   (Followers: 6)
Icarus     Hybrid Journal   (Followers: 71)
International Journal of Advanced Astronomy     Open Access   (Followers: 21)
International Journal of Astrobiology     Hybrid Journal   (Followers: 4)
International Journal of Astronomy     Open Access   (Followers: 22)
International Journal of Astronomy and Astrophysics     Open Access   (Followers: 36)
International Journal of Satellite Communications Policy and Management     Hybrid Journal   (Followers: 15)
International Letters of Chemistry, Physics and Astronomy     Open Access   (Followers: 8)
ISRN Astronomy and Astrophysics     Open Access   (Followers: 14)
Journal for the History of Astronomy     Full-text available via subscription   (Followers: 20)
Journal of Astrobiology & Outreach     Open Access   (Followers: 5)
Journal of Astronomical Instrumentation     Open Access   (Followers: 3)
Journal of Astrophysics     Open Access   (Followers: 33)
Journal of Astrophysics and Astronomy     Open Access   (Followers: 58)
Journal of Atmospheric and Solar-Terrestrial Physics     Hybrid Journal   (Followers: 133)
Journal of Geophysical Research : Planets     Full-text available via subscription   (Followers: 115)
Journal of Geophysical Research : Space Physics     Full-text available via subscription   (Followers: 134)
Journal of High Energy Astrophysics     Full-text available via subscription   (Followers: 25)
Kinematics and Physics of Celestial Bodies     Hybrid Journal   (Followers: 11)
KronoScope     Hybrid Journal   (Followers: 1)
Macalester Journal of Physics and Astronomy     Open Access   (Followers: 5)
Monthly Notices of the Royal Astronomical Society     Hybrid Journal   (Followers: 13)
Monthly Notices of the Royal Astronomical Society : Letters     Hybrid Journal   (Followers: 2)
Nature Astronomy     Hybrid Journal   (Followers: 14)
New Astronomy     Hybrid Journal   (Followers: 26)
New Astronomy Reviews     Full-text available via subscription   (Followers: 19)
Nonlinear Dynamics     Hybrid Journal   (Followers: 19)
NRIAG Journal of Astronomy and Geophysics     Open Access   (Followers: 4)
Physics of the Dark Universe     Open Access   (Followers: 4)
Planetary and Space Science     Hybrid Journal   (Followers: 106)
Planetary Science     Open Access   (Followers: 52)
Proceedings of the International Astronomical Union     Full-text available via subscription   (Followers: 2)
Publications of the Astronomical Society of Australia     Hybrid Journal   (Followers: 3)
Publications of the Astronomical Society of Japan     Hybrid Journal   (Followers: 4)
Research & Reviews : Journal of Space Science & Technology     Full-text available via subscription   (Followers: 20)
Research in Astronomy and Astrophysics     Full-text available via subscription   (Followers: 38)
Revista Mexicana de Astronomía y Astrofísica     Open Access   (Followers: 3)
Science China : Physics, Mechanics & Astronomy     Full-text available via subscription   (Followers: 4)
Science China Physics, Mechanics & Astronomy     Hybrid Journal   (Followers: 4)
Solar Physics     Hybrid Journal   (Followers: 29)
Solar System Research     Hybrid Journal   (Followers: 15)
Space Science International     Open Access   (Followers: 117)
Space Science Reviews     Hybrid Journal   (Followers: 92)
Space Weather     Full-text available via subscription   (Followers: 27)
Transport and Aerospace Engineering     Open Access   (Followers: 13)
Universe     Open Access   (Followers: 6)
Similar Journals
Journal Cover
Kinematics and Physics of Celestial Bodies
Journal Prestige (SJR): 0.328
Citation Impact (citeScore): 1
Number of Followers: 11  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1934-8401 - ISSN (Online) 0884-5913
Published by Springer-Verlag Homepage  [2469 journals]
  • Estimation of the Accuracy of Geostationary Satellite Observations

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      Abstract: — Continuous monitoring of artificial space objects requires periodic quality control of observational data. Estimating the internal accuracy of observations in the form of an RMS error of positions makes it possible to monitor and detect outliers in primary data array. For artificial satellites of the Earth, the orbital elements calculated at the Research Institute Nikolaev Astronomical Observatory (RI NAO) can be externally compared with the data of the International Laser Ranging Service (ILRS) or the Global Navigation Satellite System (GNSS). Such a comparison makes it possible to detect time synchronization problems and to identify and evaluate systematic errors. At the RI NAO, regular observations of artificial satellites in different orbits using several telescopes have been carried out for more than 10 years, and a catalog of orbital elements in the two-line element (TLE) format is maintained. The software for calculating orbital elements has been developed in cooperation with the Astronomical Observatory of the Odessa National University. This article presents the analysis of the processing results of an array of observations from 149 geostationary satellites (GSS’s). The observations have been made during 2020…2021 using the RI NAO telescope complex. Time synchronization has been provided by the Resolution-T GPS receiver with an RMS error of 40 ns. All GSS observations have been carried out using the combined observation method developed at the RI NAO. A total of 134 461 GSS positions have been obtained for which the residual O–C differences with respect to the orbit calculated at the RI NAO have been determined. The RMS error of the GSS positions in the apparent magnitude range 9m…13m is 0.5″ in right ascension and declination. A comparison of the GSS orbital positions calculated from the RI NAO orbital elements and the ILRS website data shows that the differences between the corresponding geocentric Cartesian coordinates at the start of the prediction are dX = 0.72 km, dY = –0.52 km, and dZ = 1.28 km.
      PubDate: 2022-04-01
       
  • Seasonal Features of the Spatial Distribution of Atmospheric Gravity Waves
           in the Earth’s Polar Thermosphere

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      Abstract: — The features of the spatial distribution of atmospheric gravity waves (AGW) in the polar thermosphere of the Earth are investigated. The research is based on data from direct satellite measurements of the parameters of the neutral atmosphere. According to satellite data, the amplitudes of AGWs that are systematically observed in the polar regions of both hemispheres are usually several times higher than the amplitudes of these waves in the middle and low latitudes. At the same time, the polar AGWs of large amplitudes are recorded against the background of high-speed spatially inhomogeneous wind flows, which indicates their possible amplification caused by interaction with the wind. Based on the analysis of measurement data on the Dynamics Explorer 2 satellite, the relationship between the spatial distribution of the atmospheric gravitational waves and the auroral oval has been revealed. On a large volume of experimental data, seasonal patterns of the distribution of the wave field over the Antarctic and the Arctic have been established. A comparative analysis of the features of the AGWs in the polar thermosphere of both hemispheres for the conditions of the polar day and polar night has been carried out. Some differences in the distribution of the AGWs were noted depending on the Kp-index. It has been suggested that the observed seasonal features of the AGW distribution and its dependence on the level of geomagnetic activity are associated with the restructuring of the polar wind circulation when the conditions of solar illumination and geomagnetic conditions change.
      PubDate: 2022-04-01
       
  • Ionospheric Processes during the Partial Solar Eclipse above Kharkiv on
           June 10, 2021

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      Abstract: — A solar eclipse (SE) provides a researcher with a rare opportunity to follow the dynamics of the Earth’s system (its shells)—the atmosphere, the ionosphere, and the magnetosphere—and variations in the geophysical fields over an interval of a few hours. Different solar eclipses induce significantly different disturbances in this system. The parameters of these disturbances depend on the onset time of a solar eclipse, the state of space weather, the season, the solar cycle phase, the geographic coordinates, and the degree of the solar disk occultation during a solar eclipse. It should be kept in mind that each of the SEs exhibits its own individual characteristics. The purpose of this paper is to analyze the results of ionosonde observations of the ionospheric disturbances accompanying the SE above the city of Kharkiv on June 10, 2021. At the city of Kharkiv, the maximal observed magnitude of the SE was Мmax ≈ 0.11 (more precisely, 0.112) and the relative area of the solar disk occultation was Аmax ≈ 4.4%. The eclipse started at 10:42 UT (13:42 LT) and ended at 12:12 UT (15:12 LT). The maximal magnitude was observed at 11:28 UT (14:28 LT). To study the features of variations in the virtual heights and the frequencies, we used a digital ionosonde located at the Radio Physical Observatory of the V. N. Karazin Kharkiv National University. The analysis of the space weather showed that, during the SE, as well as at the reference time intervals on June 6 and 9, 2021, the space weather conditions were favorable for observing wave disturbances, which is evidenced by the index value Kp ≈ 0.3. The frequency and altitude characteristics of the ionosphere obtained by vertical sounding were analyzed, and the features of the ionospheric processes, which accompanied the partial SE but were absent on the reference day, were determined. During the SE, wave activity in the ionosphere became stronger. The wave trains, which were observed at an altitude of the F2 layer maximum, had periods of 5 and 14 min, while the relative amplitudes of oscillations in the electron density were 0.6 and 1.25%, respectively. At an altitude of 240 km, the relative amplitude of waves with a period of ~14 min increased by 3%. The 14-min period pertains to the atmospheric gravitaty waves, while the 5-min period pertains to the waves of electromagnetic nature. A sharp and considerable increase (from 380 to 560 km) in the virtual height of the radio wave reflection from the F2 region was observed close to the moment of the greatest SE magnitude. A weak decrease (by less than 3.3%) in the electron density, which lagged behind the maximal eclipse magnitude by 12.5 min, was detected. The rates of the electron loss (1.33 × 10–3 s–1) and the ion production (3 × 108 m–3s–1) were estimated.
      PubDate: 2022-04-01
       
  • Analysis of Actinium Abundances in the Atmosphere of Cepheid HIP13962

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      Abstract: Actinium is a radioactive element that has an isotope 227Ac with the longest half-life of 21.772(3) years. It is the third element in the actinoid group, in addition to thorium and uranium, the abundance of which can be studied in the atmospheres of stars. Its presence in the atmosphere of a particular star primarily indicates some mechanism of its production. The first studies of the actinium absorption lines in the spectra of certain stars showed that the appearance of actinium in their spectrum is associated with the presence of deformation of strong lines, such as hydrogen lines and sodium doublet lines. In some cases, profiles of strong lines contain emission components. In the search for actinium absorption lines in the stellar spectra, attention was focused on such class of stars as Cepheids, which are characterized by deformation of strong lines due to pulsations. The absorption lines of actinium were studied in the spectral interval of 378.0–887.7 nm for the runaway star and Cepheid HIP13962 using the spectra obtained in 2014 with a 1.8-m telescope at Bohyunsan Optical Astronomical Observatory (BOAO, South Korea) with a spectral resolution greater than R = 80 000. The archived HIP13962 spectrum for 1995 in the wavelength range of 400.0–680.0 nm with a spectral resolution R = 42 000, which was obtained with the 1.93-m telescope of the Haute Provence Observatory (France), was also used. The modeling showed that the actinium abundance in the atmosphere of HIP13962 log N(Ac) = –1.2 on the hydrogen scale log N(H) = 12.0, with the model atmosphere Teff = 5930 K, log g = 1.0, Vmicro = 6 km s–1. This value turns out to be 0.2 more at an increase in the effective temperature Teff = 6250 K: logN(Ac) = –1.0 on the hydrogen scale logN(H) = 12.0.
      PubDate: 2022-04-01
       
  • Convective Line Shifts in the Spectra of Solar-Type Stars

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      Abstract: The Doppler line shifts in the spectra of the Sun and stars with effective temperatures from 4800 to 6200 K were measured and the average convective (granulation) velocities were estimated. The absolute scale of the line shifts for the stars was established on the basis of the derived dependence of the shifts of solar lines on optical depth. For FGK solar-type stars, curves of convection velocities as a function of the altitude in the atmosphere in a large range of altitudes from 150 to 700 km were obtained for the first time. All these curves indicate a decrease in blue shifts with altitude, which means that the granulation velocities through the photosphere slow down to zero. In the lower chromosphere, red shifts of strong Mg I lines are observed, which indicate a change in the direction of granulation velocities to the opposite and confirm the effects of reversal of granulation at altitudes above 600 km. In cooler K stars, granulation shifts change with altitude on average from –150 to 100 m/s, while they change more sharply in hotter FG stars from –700 to 300 m/s. The gradient of the line shift curves increases with an increase in the effective temperature and a decrease in gravity, metallicity, and age of the star. The convective velocity of the star averaged over all analyzed altitudes increases from –90 to –560 m/s from colder to hotter stars. It correlates with macroturbulence, asymmetry of spectral lines, and the rotation velocity of the star. We also obtained the radial velocities of the stars and compared them with the SIMBAD data. Large deviations of –21 050 and 1775 m/s were found for the stars HD 102361 and HD 42936, respectively. For the rest of the stars, the deviation does not exceed ±340 m/s, which is probably associated with the use of an average granulation velocity of –300 m/s in the SIMBAD data. Our analysis has shown that the average granulation velocity is not the same for solar-type stars. It is lower in colder stars and higher in hotter stars than the Sun. Therefore, determination of the radial velocities needs to take into account the individual granulation velocities of stars.
      PubDate: 2022-04-01
       
  • Mykola Evdokymov (1868–1941): Founder of Astrometric Research at Kharkiv
           Astronomical Observatory

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      Abstract: An analysis is presented of the scientific research accomplished by Ukrainian astronomer Mykola Evdokymov, a specialist in the field of astrometry. The astronomer’s main works, carried out using a Repsold meridian circle, are dedicated to determining stellar parallaxes, the positions of zodiacal and faint circumpolar stars, and the positions of large planets. At Kharkiv Astronomical Observatory, Evdokymov conducted systematic observations of the following objects and phenomena: solar and lunar eclipses, including as a member of the observatory’s expeditions during the total solar eclipses of 1914 and 1936; comets (Halley, Delavan, Stearns, Pons–Winnecke); and meteor showers. He participated in determining the positions of reference stars for the asteroid (433) Eros. He conducted systematic studies of the meridian circle, developed new astronomical instruments, organized the functioning of a time service at the observatory, and carried out the determination of star declinations by measuring the sums and differences of the zenith distances of star pairs by the Sanders–Raymond method (using a meridian circle and a transit instrument).
      PubDate: 2022-04-01
       
  • Geomagnetic Effect of the Solar Eclipse of June 10, 2021

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      Abstract: A solar eclipse (SE) pertains to rare high-energy natural phenomena. For instance, a change in the internal (thermal) energy of the air in a layer only 100 m in height attains 1018 J while the power of the process is on the order of terawatts. The energy of the processes produced by the SE in the upper atmosphere and geospace is significant. For instance, the thermal energy of the ionospheric plasma in a volume of ~1019 m3 decreases by 1011 J. The magnetic field in a volume of ~1021 m3 decreases by 50 nT, and its energy by 1015 J. SEs are accompanied by disturbances in all subsystems of the Earth–atmosphere–ionosphere–magnetosphere system. Disturbances in the upper atmospheric and ionospheric parameters act to inevitably produce geomagnetic field variations. At present, geophysicists have no consensus on how SE manifests itself in the geomagnetic field. The available data are inconsistent. Most of the researchers believe that the geomagnetic effect of SE exists. In some cases, the temporal variations in the geomagnetic field, as a whole, repeat the changes in the illumination of the Earth’s surface; in other cases, they may be ahead or delayed by ~1 hour in relation to the changes in illumination. Most often, the geomagnetic effect is studied in the region of the total SE where it should be the most pronounced. The further the observatory is located from the umbra, the more difficult it is to relate the magnetic variations to the SE. Finding the response of the geomagnetic field to the SE is a complicated task. A possible response is “masked” by variations of another nature. Moreover, the magnitude and sign of the geomagnetic field disturbance significantly depend on the state of space weather, season, local time, location of the magnetic observatory, and, of course, the magnitude of the eclipse. Therefore, the study of the effect of SEs on the geomagnetic field remains an important task. The purpose of this study is to present the results of analysis of temporal variations in the geomagnetic field observed by the International Real-Time Magnetic Observatory Network (INTERMAGNET) during the SE of June 10, 2021. The main feature of this eclipse was that the SE was annular (maximum magnitude Mmax ≈ 0.943). The annular SE occurred on June 10, 2021 with a commencement time 08:12:20 UT over Canada. The Moon’s shadow moved across the Atlantic Ocean, Greenland, the Arctic Ocean, the North Pole, and the northern parts of Europe and Asia. A partial SE occurred in Mongolia and China, and it ceased at 11:33:43 UT. The annularity was observed from 10:33:16 to 10:36:56 UT over Greenland. The analysis of the geomagnetic effect was based on the INTERMAGNET database. The data were processed with 1-min temporal resolution and 0.1-nT level resolution, and temporal variations in the X, Y, and Z components recorded at 15 magnetic observatories were studied. The SE was found to be accompanied by an aperiodic decrease in the X component by 31–36 to 2–3 nT. A decrease in this level attained a maximum value during the maximum magnitude of the annular eclipse, and the magnitude of the effect rapidly decreased with distance southward. For the southernmost observatories, we were not able to determine a decrease in the mean value. Other geomagnetic field components had hardly any change in the course of the SE. The SE was also accompanied by quasi-periodic variations in the level of the X component. The amplitude of these variations decreased from 4 to 1 nT with distance away from the region of the annular eclipse. The period of the quasi-periodic disturbances was observed to be 40 ± 2 min. These disturbances are suggested to be produced by atmospheric gravity waves under the action of the solar eclipse. The relative changes in the atmospheric gravity wave pressure were estimated to be ~1–2%. The estimates of both aperiodic and quasi-periodic effects are in agreement with the observations, which confirms the mechanism for their generation.
      PubDate: 2022-01-01
      DOI: 10.3103/S0884591322010020
       
  • Kamchatka Meteoroid Effects in the Geomagnetic Field

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      Abstract: The data acquired at ten geomagnetic observatories (Paratunka, Magadan, Yakutsk, and Khabarovsk (the Russian Federation); Memambetsu, Kanoya, and Kakioka (Japan); Cheongyang (Republic of Korea); Shumagin and College (USA)) during the Kamchatka meteoroid event of December 18, 2018, and on the reference days of December 17 and 19, 2018, have been used to analyze temporal variations in the geomagnetic field components. The distance r from the observatories to the site of explosive energy release by the meteoroid varied from 1.001 to 4.247 Mm. The passage of the Kamchatka meteoroid through the magnetosphere and atmosphere was accompanied by variations mainly in the H geomagnetic field component. The magnetic effect from the magnetosphere was observed to occur twice, 51 and 28 min prior to the meteoroid explosion; the amplitude of the disturbances in the geomagnetic field did not exceed 0.2–1 nT, and the durations were observed to be approximately 20 and 10 min, respectively. Alternating peaks in the level of the H component were observed to lag behind the meteoroid explosion by 8 to 13 min for r from 1.001 to 4.247 Mm. The amplitude of the oscillations varied with increasing r from ~0.5 to ~0.1 nT, while the duration of the magnetic effect from the ionosphere varied in the 16–25-min range for all distances. The apparent speed of propagation in this group of disturbances that were of MHD nature was observed to be approximately 10 km/s. In the second group of disturbances, the time lag increased with increasing distance within the distance range mentioned above from 56 to 218 min. The duration of the disturbance was approximately 16–65 min, the apparent speed was 336 m/s, and the period was 5–10 min. This disturbance in the magnetic field was caused by an atmospheric gravity wave propagating from the meteoroid explosion. The theoretical models for the magnetic effects observed are presented and theoretical estimates are performed. The observations are in agreement with the estimates.
      PubDate: 2022-01-01
      DOI: 10.3103/S0884591322010032
       
  • Comparison of Ground-Based and Satellite Geomagnetic Pulsations during
           Substorms

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      Abstract: — 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.
      PubDate: 2022-01-01
      DOI: 10.3103/S0884591322010044
       
  • Results of Observations of Wave Motions in the Solar Facula

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      Abstract: — The results of spectropolarimetric and filter observations of the facular region in the lines Fe I 1564.3, Fe I 1565.8 nm, Ba II 455.4 nm, and Ca II H 396.8 nm obtained near the center of the solar disk at the German Vacuum Tower Telescope (Tenerife, Spain) are discussed. It is shown that the facular contrast at the center of the Ca II H line increases more slowly as the magnetic field strength increases and, then it begins to decrease if the field increases further. It is concluded that the reason for such behavior is the nonlinear height dependence of the line source function due to the deviation from the local thermodynamic equilibrium. It is found that waves propagating both upward and downward can be observed in any area of the facula, regardless of its brightness. In bright areas with a strong magnetic field, upward waves predominate, while downward waves are more often observed in less bright areas with a weak field. It is shown that the facular contrast measured at the center of the Ca II H line correlates with the power of wave velocity oscillations. In bright areas, it increases with the power regardless of the direction in which the waves propagate. In facular regions with decreased brightness, the opposite dependence is observed for both types of waves. In turn, the power of wave velocity oscillations is sensitive to the field strength magnitude. In the magnetic elements of the facula with increased brightness, the stronger the field, the higher the power of oscillations of both upward and downward waves. In areas with decreased brightness, the inverse dependence is observed. It is concluded that the contrast increase with the increase in the power of wave velocity oscillations observed in bright areas of the facula can be considered as evidence that these areas look bright not only because of the Wilson depression but also because of the heating of the solar plasma by the waves.
      PubDate: 2022-01-01
      DOI: 10.3103/S0884591322010056
       
  • Convection Effect in the Surface Atmosphere of Solar Eclipses of March 20,
           2015, and June 10, 2021

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      Abstract: 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.
      PubDate: 2021-11-01
      DOI: 10.3103/S0884591321060039
       
  • Thermal Effect in Surface Atmosphere of the Solar Eclipse on June 10, 2021

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      Abstract: 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.
      PubDate: 2021-11-01
      DOI: 10.3103/S0884591321060040
       
  • Identification of Acoustic-Gravity Waves According to the Satellite
           Measurement Data

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      Abstract: 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.
      PubDate: 2021-11-01
      DOI: 10.3103/S0884591321060052
       
  • The Fe IX Line at 17.1 nm in the Radiation Spectrum of Slow
           Magneto-Acoustic Waves Propagating in the Solar Corona

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      Abstract: — 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 Δλd = 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 vd and the velocities of nonthermal motions vnt 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.
      PubDate: 2021-11-01
      DOI: 10.3103/S0884591321060064
       
  • Statistical Analysis of the Orbital Motion of Selected Artificial Earth
           Satellites during Solar Cycle 24

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      Abstract: — 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 F10.7 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 F10.7 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.
      PubDate: 2021-11-01
      DOI: 10.3103/S0884591321060027
       
  • Ludwig von Struve (1858–1920): Development of Positional Astronomy at
           the Kharkiv Astronomical Observatory

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      Abstract: 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.
      PubDate: 2021-09-01
      DOI: 10.3103/S0884591321050032
       
  • Pole Coordinates and Length of Day from Laser Ranging of Low Earth
           Orbiters

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      Abstract: 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.
      PubDate: 2021-09-01
      DOI: 10.3103/S0884591321050068
       
  • Molecular Hydrogen H2 (4-0) in the Spectra of Jupiter and Saturn

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      Abstract: 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.
      PubDate: 2021-09-01
      DOI: 10.3103/S0884591321050020
       
  • Attenuation of Evanescent Acoustic-Gravitational Modes in the
           Earth’s Thermosphere

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      Abstract: — 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.
      PubDate: 2021-09-01
      DOI: 10.3103/S0884591321050044
       
  • Dynamic Falling of the Chelyabinsk Meteoroid: Sizes, Radiation, and
           Destruction

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      Abstract: 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.
      PubDate: 2021-09-01
      DOI: 10.3103/S0884591321050056
       
 
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