Kinematics and Physics of Celestial Bodies最新文献

A solar eclipse (SE) causes recordable disturbances in all subsystems of the Earth–atmosphere–ionosphere–magnetosphere system and in geophysical fields. The response of the system to an SE substantially depends on the eclipse magnitude, the solar cycle phase, the atmospheric and space weather, the season, the time, and the observation coordinates. Manifestations of the response are also influenced by the observation technique. Despite the fact that the effect of a solar eclipse on the ionosphere has been studied for approximately 100 years, a number of unresolved issues remain. The purpose of this study is to describe the results of our analysis of temporal total electron content (TEC) variations caused by the annular solar eclipse on June 21, 2020, in the equatorial ionosphere. The authors analyzed 132 time dependences of the TEC that covered an extensive region with an eclipse. The maximum magnitude (M_max = 0.9940) of the eclipse, which began at 06:39:59 UT, was observed in northern India in Uttarakhand and lasted 38 s. Space weather conditions on June 21, 2020, were favorable for studying the effects associated with the SE. To reveal the response of the ionosphere to the annular SE on June 21, 2020, the GPS signal recordings were processed. Time variations of the TEC in the ionosphere on reference days and on the SE day of June 21, 2020, were analyzed on a global scale. For this purpose, the results of measurements at twelve stations and eleven GPS satellites were used. The dependences of the absolute and relative TEC value decreases caused by the SE on a time of day are studied. The lowest value of the TEC decrease (–2…–3 TECU) was observed in the morning. In the daytime and in the evening hours, it reached –4…–6 TECU. The relative decrease in the TEC barely depended on a time of day and reached –30…–35%. No stable dependence of the TEC decrease on the eclipse magnitude was found. The relative value of the TEC decrease depended on the SE magnitude, i.e., smaller values of the SE magnitude corresponded to smaller values of the relative TEC decrease. The duration of the TEC reduction exceeded the duration of the eclipse by 1.5–2.5 h. The time of reaching the minimum TEC values in the daytime and the evening hours delayed by 10–20 min with respect to the time of reaching the maximum SE magnitude. Wave-like disturbances of the TEC were practically absent. Undisturbed TEC values and the TEC values disturbed by the eclipse substantially depended on the location of stations and the trajectory of satellites, which was associated with the influence of equatorial ionization anomaly. This is the main peculiarity of ionospheric effects of the SE at latitudes 0°–30° N.

From January 29, 2017 to May 16, 2020 (GPS weeks 1934–2105) all products of the International GNSS Service (IGS)–precise ephemerides of GPS and GLONASS satellites, coordinates and velocities of permanent GNSS stations, etc.–were based on the IGS14 reference frame, the first IGS realization of the release of the International Terrestrial Reference Frame ITRF2014. Observations of GNSS satellites at permanent stations located in Ukraine and in the Eastern Europe for this period were processed in the GNSS Data Analysis Centre of the Main Astronomical Observatory NAS of Ukraine (MAO). The processing was carried out with the Bernese GNSS Software ver. 5.2 according to the requirements of the EUREF Permanent GNSS Network (EPN), that were relevant at that time. In total, observations on 277 GNSS stations, including 205 Ukrainian stations belonging to the following operators of GNSS networks: MAO NAS of Ukraine, StateGeoCadastre of Ukraine (UPN GNSS), NU Lviv Polytechnic (GeoTerrace), PJSC System Solutions (System.NET), TNT TPI company (TNT TPI GNSS Network), Navigation and Geodetic Center (NGC.net), UA-EUPOS/ZAKPOS, E.P.S. LLC, Coordinate navigation maintenance system of Ukraine (NET.Spacecenter), Kiev Institute of Land Relations (KyivPOS), KMC LLC, were processed. The IGS14 reference frame was realized by applying No-Net-Translation conditions on the coordinates of the EPN Class A stations from the EPN C2100 catalogue. As result, the stations’ coordinates in the IGS14 reference frame and the zenith tropospheric delays for all stations were estimated. The mean repeatabilities for components of GNSS stations’ coordinates for all weeks (the characteristics of the precision of the obtained daily and weekly solutions) are in the following ranges: for the northern and eastern components – from 0.6 to 1.4 mm (average values are 0.93 and 1.00 mm respectively) with outliers for the eastern component of 2.02 and 1.55 mm for GPS weeks 2085 and 2091 respectively, for height component – from 2.0 to 5.5 mm (average value is 3.51 mm).

The photometric flattening index as a quantitative characteristic of the shape of the solar corona observed during a total solar eclipse was proposed by Ludendorff in the 1930s. The work collected the values of the flattening index for 69 total solar eclipses in 1851–2020 and investigated their relationship with the parameters of the solar cycle. The value of the flattening index varies from approximately 0.3–0.4 at the cycle minimum to 0.0–0.1 at the cycle maximum. The flattening index correlates with the relative sunspot numbers and the phase of the solar cycle. The correlation coefficients between the flattening index and the daily, monthly and smoothed monthly sunspot numbers are –0.577 (р < 4 × 10^–7), –0.595 (p < 8 × 10^–8) and –0.598 (p < 7 × 10^–8), respectively. The correlation coefficients between the flattening index and the phase of the solar cycle for the rising and declining phases of the cycle are –0.759 (p < 5 × 10^–6) and 0.660 (p < 2 × 10^–6), respectively. The observed shape of the solar corona, in particular the value of the flattening index, is determined by the global magnetic field of the Sun, mainly by its dipole component.

A mechanism for the origin of Kuiper belt (KB) bodies different from the hitherto known mechanisms is proposed. The distributions of the orbital elements of most of the bodies of the hot component of the KB are analyzed. The shape of the distributions indicates that all of these bodies could have appeared as a result of the destruction of a single massive body (Kuiper belt planet, KBP). The separation velocities of the fragments were determined mainly by the linear velocities of the parts of the KBP at different depths and latitudes. The maximum separation velocity corresponded to the linear velocity on the surface of the KBP near the equator and could be 2.4 km/s. The size of the KBP could be either slightly smaller or larger than the size of the Earth. The spin period was approximately 4 h. The KBP spin axis was inclined at a slight angle to the ecliptic plane, and it was directed toward the Sun at the time of destruction. This mechanism is in good agreement with current observational data. It can explain the large number of bodies with satellites in the KB as well as the revealed dependence of the average density of bodies on their size. According to this mechanism, the spin axes of the formed debris (primarily large ones) should be inclined at small angles to the ecliptic plane. The spin axes of the dwarf planets Pluto and Haumea are inclined to the ecliptic plane at angles of 23° and 10°, respectively. The future data on the coordinates of the poles of other large KB bodies can become the final confirmation of the proposed mechanism.

A comprehensive modeling of the processes in all geospheres caused by the fall and explosion of the Yushu meteoroid in the Qinghai Province (People’s Republic of China) on December 22, 2020, was performed. The magnetic, electrical, electromagnetic, ionospheric, and seismic effects, as well as the effects of acoustic-gravity waves, were estimated. It is shown that the magnetic effect of turbulence was insignificant. The magnetic effect of the ionospheric currents and the current in the meteoroid’s wake could be significant (~1 nT). Due to the capture of electrons in the field of the atmospheric gravity wave, the magnetic effect could reach the order of 1 nT. The effect of the external electric field could lead to a short-term current pulse of up to 10⁴ A. The electrostatic effect could be accompanied by the accumulation of a charge of 1–10 mC with an electric field strength of approximately 1 MV/m. The flow of electric current in the wake could lead to the emission of an electromagnetic pulse in the frequency range of approximately 10 kHz with a strength of 3–30 V/m. It was found that the electromagnetic effect of infrasound could be significant (approximately 3–20 V/m and 10–60 nT). Absorption of the shock wave at the heights of the dynamo region of the ionosphere (100–150 km) could be accompanied by the generation of secondary atmospheric gravity waves with a relative amplitude of 0.1–1. The passage of the meteoroid led to the formation of a plasma wake and to a noticeable disturbance of not only the lower but also the upper atmosphere at distances of at least 1000 km. The occurrence of an electrophonic effect seems unlikely. The possibilities of generating ion and magnetic sound by infrasound as well as gradient-drift and drift-dissipative instabilities are discussed. The magnetic, electrical, and electromagnetic effects discussed in this article partially fill in the gaps in the theory of the physical effects of meteoroids in the Earth–atmosphere–ionosphere–magnetosphere system. The magnitude of the earthquake caused by the meteoroid explosion did not exceed 2.5. The average fall rate of celestial bodies similar to the Yushu meteoroid is 0.49 year^–1.

A comprehensive modeling of the processes in all geospheres caused by the fall and explosion of the Yushu meteoroid in the Qinghai Province (People’s Republic of China) on December 22, 2020, was performed. Thermodynamic and plasma effects, as well as the effects of the plume and turbulence, accompanying the passage of the Yushu meteoroid were estimated. It is shown that the passage of the celestial body led to the formation of a gas and dust plume. The heated meteoroid wake cooled down for several hours. Four stages of cooling of the meteoroid wake are considered. The first of them lasted approximately 0.2 s, and the temperature of the wake decreased by half due to radiation. During the second stage (~3 s), cooling continued due to radiation and expansion of the wake, and the temperature decreased by 20%. During the third stage, which lasted 6 s, the explosion products and heated gas (thermal column) with an acceleration of approximately 30 m/s² rose at a speed of 140 m/s, and the temperature decreased by 10%. The fourth stage lasted approximately 50 s, the thermal column intensively absorbed cold air, gradually cooled, and slowed down. The maximum height of the thermal column reached 7–8 km. The explosion products (dust particles and aerosols) that were part of the thermal column were subsequently involved in three processes: slow settling to the Earth’s surface, turbulent mixing with the surrounding air, and transportation by prevailing winds around the planet. It is shown that the effect of turbulence in the meteoroid’s wake was well expressed, while magnetic turbulence had hardly any effect. The main parameters of the plasma in the wake are estimated: height dependences of the linear and volume electron densities, values of their relaxation times, particle collision frequencies, plasma specific conductivity, and relaxation times of the electron temperature. It is shown that the linear and volume electron densities in the wake at the initial moment were 10¹⁹–4 × 10²² m^–1 and 10¹⁷–10²¹ m^–3 and the plasma specific conductivity was of the order of 10³ Ω^–1m^–1. The role of the dust component of the plasma is discussed.

The photometric characteristics in the midinfrared range of compact galaxies with ionizing radiation leakage (LyC galaxies) are studied to find relationships that would enable the quantitative assessment of the ionizing radiation that goes beyond the galaxy. In particular, the relationships between the color characteristics of galaxies according to data from the WISE space telescope and radiation fraction f_esc(LyC) in the Lyman continuum and radiation fraction f_esc(Ly_α) in the Ly_α line, which go beyond the galaxy, are investigated. The dependences of f_esc(LyC) and f_esc(Ly_α) on color index W1–W4 are established from the WISE space telescope data, where W1 and W4 are apparent stellar magnitudes at wavelengths of 3.4 and 22 μm, respectively. This makes color index W1–W4 a useful indicator for quantifying f_esc(LyC) and f_esc(Ly_α) in addition to the previously established some characteristics of LyC galaxies in the optical and ultraviolet ranges. Thus, the radiation of galaxies in the midinfrared range can be used to search for candidates for leaking LyC galaxies with the purpose of their further observations.