Kinematics and Physics of Celestial Bodies最新文献

This study is aimed at comprehensively analyzing and estimating the effects in gas dynamics, as well as mechanical and optical effects, from the Kyiv meteoroid that entered the terrestrial atmosphere and exploded over Bila Tserkva raion, Kyiv oblast (Ukraine). According to the International Meteor Organization (IMO), the apparent magnitude of the meteoroid was –18. According to our estimates, the luminous power was 215 GW with an effective duration of 2.4 ± 0.2 s, the total luminous energy was 25.2 ± 2.5 GJ, and the initial kinetic energy was 0.09 ± 0.01 kt of TNT or 375 ± 35 GJ. The initial mass of the cosmic body was estimated to be 0.89 ± 0.09 t, the volume was 0.250 ± 0.025 m³, and the size was 79 ± 3 cm. The initial velocity of the meteoroid reached 29 km/s. The inclination angle, i.e., the angle that the trajectory makes with the horizontal plane, was 32°. The explosion altitude equal to 38 km and the inclination angle equal to 32° give an estimate of 3.5 t/m³ for the material density, which is close to the rock density. The energy of the processes, the gas dynamics effects, and the mechanical and optical effects from the celestial body have been analyzed. The main release of energy associated with the deceleration of the fragments of the celestial body, which was defragmented under a dynamical pressure of approximately 2.5 MPa, took place in the region with a length of 2 km at an altitude of approximately 38 km. A quasi-continuous defragmentation is suggested to produce a mass distribution that follows a power law. The main parameters of the ballistic and explosive shock waves have been estimated. For the Mach number of 97, the radius of the ballistic shock wave is estimated to be approximately 77 m, and the fundamental period to be 0.7 s, which showed a dispersive increase from 3.7 to 11.5 s with the propagation path length increasing from 50 to 5000 km. The radii of cylindrical and spherical wavefront shock waves were approximately 0.28 and 0.34 km, and their fundamental periods were approximately 2.6 and 3.2 s, respectively. These periods increased from 9.5 to 30.0 s and from 11.1 to 35.1 s with an increase in the propagation path length from 50 to 5000 km. In the vicinity of the meteoroid’s explosion height, the relative excess pressure was a maximum. It decreased with a decrease in the altitude and increased with an increase in the altitude up to approximately 120–150 km, at which it attained values of approximately 6–7% and then further decreased down to a few percent. The absolute value of the excess pressure is estimated to be near the altitude of the explosion; subsequently it decreased with a decrease in the altitude down to 20–25 km and then increased further again. At the epicenter of the explosion, it is estimated to be approximately 94 Pa for the cylindrical wavefront and approximately 99 Pa for the spherical wavefront, which is not enough to damage objects on the ground. The excess pressure decreased

The Tonga volcano is among the five most powerful volcanoes in the world. The explosion of the Tonga volcano on January 15, 2022, was unique. It has led to disturbances in the lithosphere, World Ocean, atmosphere, ionosphere, magnetosphere, and all geophysical fields. A number of studies have been devoted to the disturbance of the Earth’s magnetic field. The transport of magnetic field disturbances by atmospheric gravity waves and tsunamis, disturbances in magnetically conjugated regions due to acoustic resonance, the effect on the equatorial electrojet, etc., have been studied. This is far from the end of the variety of magnetic effects of the Tonga volcano. This study is aimed at describing the results of the analysis of global bay disturbances in the geomagnetic field observed after the Tonga volcano explosion on January 15, 2022. The results of measuring the temporal variations in the level of the X, Y, and Z components by the INTERMAGNET world network of stations are used as initial data. The analysis of the magnetic data is preceded by an analysis of space weather conditions. A preliminary analysis of temporal variations in the level of the X-, Y-, and Z-components indicates that these variations on the reference days are smoother than on January 15, 2022. An analysis of the temporal variations in the level of the X-, Y-, and Z-components of the geomagnetic field and a statistical analysis of the disturbance parameters have shown the following. Bay disturbances of all components of the geomagnetic field are observed with a time delay that varies depending on the distance to the volcano from several tens of minutes to 100–200 min. The magnitude of the effect varies from approximately 10 to approximately 60 nT. The largest disturbances occur in the Y component. The delay time and duration of disturbances increase with an increase in the distance from the volcano, while their amplitude, on the contrary, decreases. The speed of propagation of bay disturbances is close to the speed of the blast wave. Bay disturbances are weakly expressed or completely absent on the night side of the planet. It is substantiated that bay disturbances are closely related to the occurrence of an ionospheric hole under the action of a blast wave from the volcano. The results of estimates of bay disturbances are in good agreement with the observation results.

We present the results of the study of the magnetic field in the active prominence on July 24, 1999 at 07:00 UT, using the observational material obtained on the Echelle spectrograph of the horizontal solar telescope of the Astronomical Observatory of Taras Shevchenko Kyiv National University. Our analysis is based on the study of I ± V profiles of the Hα line, which were related to heights in the range of 11–20 Mm. It was found that the bisectors of the I ± V profiles are non-parallel to each other in majority of places of this prominence. This indicates the inhomogeneity of the magnetic field: with a uniform magnetic field, the named bisectors should be parallel. Moreover, the maximum splitting of bisectors is observed not only in the core of the line (which was found earlier by other authors), but also in its far wings, at distances of 1.5–2.5 Å from the line center. The specified maximum of splitting corresponds to magnetic field of about 3000 G, but this value should be considered only as a lower estimate of the true local magnetic fields. In particular, the second maximum of bisector splitting may indicate that the actual value of Zeeman splitting in small-scale structures with a small filling factor reaches the above value of 1.5–2.5 Å which corresponds to the field strength of almost 100 kG. From our study it follows that evidences on such extremely magnetic fields may not actually be a rare phenomenon, but a rather common one, which, however, can be recorded only under certain favorable observational conditions.

Acoustic gravity wave modes in the Earth’s thermosphere, the amplitude of which does not depend on height, are theoretically investigated. These studies are stimulated by satellite observations, according to which the amplitudes of acoustic gravity waves in the polar thermosphere do not show dependence on height in the altitude range of 250–450 km. It is shown that the propagation of acoustic gravity wave modes with the height-independent amplitude should be considered as an oscillatory process that occurs simultaneously at two natural frequencies. The dispersion equation for these waves is obtained. According to the frequency–wave vector diagnostic diagram, the dispersion dependence of waves with the constant amplitude is in the region that is prohibited for free propagation. It separates the waves propagating horizontally, in which the amplitude in the vertical direction increases from waves with the amplitude decreasing in the vertical direction. Solutions are found for the perturbed quantities in the two-frequency mode of oscillations. It is noted that the superposition of a few of such modes can lead to the emergence of complex resulting motions close to turbulent ones. It is shown that there is a selected quasi-harmonic mode with the constant amplitude, which is characterized by a fixed frequency and wavelength. It is concluded that this kind of wave mode with the height-independent amplitude of the perturbed values prevails in the observations in the Earth’s polar thermosphere.

The dissipation in the geomagnetic tail is a process that stops the cascade transfer of energy in the inertial turbulent range and transforms the energy of turbulent motions into heating. In the case of kinetic turbulence with the dominance of the thermal pressure over the magnetic field pressure, dissipation is also possible in the inertial range. This study considers an approach for obtaining the distribution of the energy-conversion rate (multiscale spectrum) of the electromagnetic field with the preliminary involvement of the multispacecraft method for calculating the current density. For the first time, a multiscale spectrum of the energy conversion rate in the tail of the Earth’s magnetosphere is obtained and analyzed. The results of measuring the magnetic and electric fields by the MMS mission spacecraft in the region of the current stratum and during high-speed plasma flows in the plasma layer during September 8, 2021 are used.

The explosive Tonga volcano is among the unique ones. Its order of magnitude is the same as Krakatoa (1883), St. Helens (1980), El Chichón (1982), and Pinatubo (1991) volcanoes. The uniqueness of the Tonga volcano lies in the fact that the products of eruption of the Tonga volcano rose to a record height of 50–58 km, whereas the height of eruption of the most powerful Krakatoa volcano reached only 40–55 km. The Tonga volcano has estimates of 3.9 × 10¹⁸ J for thermal energy, approximately 5.8 for volcanic explosive index VEI, approximately 5.5 for volcano magnitude M, and approximately 10.8 for eruption intensity I. We have estimated the explosion energy to be 16–18 Mt TNT. The problems of proving that a decrease in the total electron content (TEC), which was observed on January 15, 2022, in the ionosphere, was caused by the Tonga volcano explosion, and determining the principal parameters of the ionospheric hole are very urgent problems. This study is aimed at analyzing the parameters of the ionospheric hole created by the Tonga volcano explosion on January 15, 2022. Well-known GPS technologies are used to obtain data on time variations of the ionospheric TEC in the vertical column by measuring the pseudo-range and the integrated phase data at two frequencies along the path to each GPS satellite. The space weather conditions were favorable for observing the ionospheric effects caused by the explosion of the Tonga volcano. The calendar dates of January 13 and 17, which are used as reference days, were the least disturbed ones. The main results are as follows. It was found that the TEC on the reference days varied almost monotonically. Aperiodic and quasi-periodic variations of TEC were observed on the day of volcano eruption. Aperiodic variations are associated with a decrease in the TEC. This effect is called the ionospheric hole. It has been proven that the ionospheric hole is caused by a volcanic explosion. The delay time of the hole increases with an increase in the distance between the volcano and the observation site, while both the absolute value of the TEC and the relative value of its decrease are reduced. According to estimates, the horizontal size of the ionospheric hole did not exceed 10 Mm, and the time delay of its appearance did not exceed 122 min. The vertical speed of disturbance propagation was 36–72 m/s, and the horizontal speed was 2.2 km/s. The lifetime of the ionospheric hole was 120–200 min. The TEC in the ionospheric hole was reduced by approximately 2.5–10 TECU, which is a function of the distance from the volcano to the observation site, and the relative decrease ranged from –17 to –34%.

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.