Kinematics and Physics of Celestial Bodies最新文献

During typhoon activity, the atmospheric gravity waves (AGWs) will cause the Earth’s ionosphere to fluctuate, causing the equivalent reflection height of the ionosphere to change, resulting in an abnormal change in the phase of the VLF signal received by the receiving station. Therefore, This paper analyses the response of phase the VLF signal to atmospheric gravity waves, using the VLF monitoring system to study the VLF signal data received by the Xinxiang receiving station during typhoon “Dan” in October 1999, which was transmitted from the Novosibirsk launching station of the Russian Alpha navigation system. Then the effect of the atmospheric gravity wave on the VLF signal propagation is studied based on the waveguide mode theory. It is calculated that when the frequency of the VLF signal is 14.9 kHz on 9 October 1999, the phase change is 5.12 cec, and the phase change on 12 and 13 October is 4.36cec and 3.34 cec respectively. Space weather conditions, and solar flare data released by the GOES satellite were then analyzed and their effect on the phase of the VLF signal was excluded. The results show that the phase anomaly of the VLF signal is caused by the atmospheric gravity wave excited by the typhoon. Therefore, the effect of atmospheric gravity waves on VLF signal propagation studied in this paper could predict and correct the phase of VLF signals, ensure the accuracy of the VLF navigation system as GPS backup, and have great significance for improving the accuracy of VLF navigation and positioning.

Ionospheric modelling is one of the most powerful tools for studying the behavior of the ionosphere. The aim of this paper is to assess the performance of IRI-Plas2017 in five different longitudinal sectors during different phases of solar cycle 24 (2011–2017). An hourly mean value of Total Electron Content (TEC) was used to study the diurnal and seasonal variations in TEC. An annual error plot profiled on monthly basis was used to study the difference between the measured and predicted TEC values. The annual TEC deviations were used to investigate the relationship between TEC derived from Global Positioning System (GPS) and IRI-Plas2017 model. Our results showed that the highest peak value of TEC was recorded as ~89 TECU (06:00UT) in the Asian sector (BAKO) while the lowest peak value of ~22 TECU (08:00UT) was recorded in the Australian sector (DAV1) in the ascending and descending phase during the March equinox respectively. Semi-Annual variation is a prevailing factor in all the solar cycle phases in the Africa and Asian sectors except during the descending and maximum phase where anomalies were recorded. Semi-annual anomalies were also prominent in all the solar cycle phases in the Australian, American, and Asian sectors. Winter anomaly was predominant in all the phases of solar cycle in the American, Asian, and European sectors. However, the IRI-Plas2017 model was not able to appropriately reproduce the two prominent phenomena (Semi-annual Variations and Winter Anomalies) observed in all the five longitudinal sectors.

This work analyzes the electromagnetic mechanism of interaction between subsystems in the Earth–atmosphere–ionosphere–magnetosphere (EAIM) system. The study is based on a system of equations for the volumetric density of electromagnetic energy and the total electron content of high-energy electrons in the magnetic flux tube, which describes the resonant interaction between waves and particles at the cyclotron frequency. The purpose of this work is to obtain analytical solutions to the system of equations describing the interaction of powerful electromagnetic radiation with high-energy magnetospheric electrons and to numerically model the main parameters of this interaction. Solutions for both the stationary and nonstationary problems have been obtained. Aperiodic and quasi-periodic modes of disturbances have been identified. The value of the stationary relative disturbance of total electron content, as a function of the particle and electromagnetic radiation source parameters, has been calculated. The dependence of various magnetospheric and ionospheric parameters on the electron and electromagnetic radiation source parameters has been determined. The radiation from a single lightning strike can lead to significant electron flux densities (~10⁵–10¹¹ m^–2 s^–1). In this case, the electron density in the ionosphere can increase from tens of percent to several hundred times. The disturbance of the geomagnetic and ionospheric electric fields, caused by ionization bursts in the ionosphere, has been calculated. The amplitude of geomagnetic field disturbances ranged from fractions to hundreds of nanoteslas, while the electric field disturbance varied from 10 μV to 100 mV. Secondary effects in the EAIM system, caused by the electromagnetic mechanism of disturbances, are briefly discussed.

The scientific and organizational activities of the prominent Ukrainian astrophysicist, planetary scientist, and academician of the Ukrainian SSR Mykola Pavlovych Barabashov are studied. The stages of the scientific path of the talented scientist, one of the founders of planetary science, who devoted his life to the study of the bodies of the Solar System, are highlighted. The ways of implementing well-known astronomical projects initiated and implemented by Academician Barabashov at Kharkiv State University in order to organize high-quality observations and improve the results obtained are analyzed. The contribution of Mykola Barabashov to the formation of planetary research in the astronomical institutions of the Soviet Union through the functioning of the Commission on Planetary Physics of the USSR Academy of Sciences, which he oversaw for many years, is considered. The photometric and, later, spectrophotometric and polarimetric studies of the Moon and planets initiated by Mykola Barabashov at the Kharkiv Astronomical Observatory led to the formation of a dynamically developing scientific school of planetary science. With the beginning of the space era in human history, the results of the activities of the representatives of the school received international recognition, as the study of solar system objects has acquired applied significance. The article characterizes the areas of works that were jointly carried out by the students and followers of Academician Mykola Barabashov at the Kharkiv Astronomical Observatory together with their scientific leader. The degree of involvement of Kharkiv astronomers under the general leadership of Mykola Barabashov in the projects of the Soviet space program in the early 1960s is determined.

This study examines the absorption lines of promethium, a radioactive element with a short half-life, in the spectra of the magnetic peculiar star HD 25 354, which belongs to the spectral class A0Vp. It also determines the promethium abundance in the star’s atmosphere. The analysis utilized an archival spectrum of HD 25 354 from the ELODIE database, obtained in 1996, covering the wavelength range of 400.0–680.0 nm, with a spectral resolution of R = 42 000 and a signal-to-noise ratio (S/N) of 100, recorded at the 1.93-m telescope at the Haute-Provence Observatory. Additionally, spectra collected by F. Musaev in 2006, using the 2-m telescope at Terskol Peak Observatory, were analyzed. These spectra covered the wavelength range of 370.0–940.0 nm, with S/N = 200 and R = 60 000. The previously determined atmospheric parameters of the star (T_eff = 12 800 K, log g = 4.15, V_micro = 0.23 km/s) and the chemical composition of its elements were used to calculate a synthetic spectrum over a wide range. This synthetic spectrum generally gave a satisfactory approximation of the observed spectrum. By comparing the synthetic spectrum of HD 25 354 with the observed data, 11 lines of promethium were identified, and its abundance was determined. The promethium abundance was found to be consistent with the abundance levels of other lanthanides, with a value of log N = 5.8–5.9 on the hydrogen scale, where log N(H) = 12. According to literature data, the promethium abundance in the atmosphere of HR 465 (log N = 5.05) is also within the range of lanthanide abundance.

Longitudinal, latitudinal, and altitudinal features of the zonal wind in the Northern Hemisphere under the influence of 27-day variations of solar activity (SA) were studied. The research aims to improve the accuracy of weather forecasts and deepening our knowledge about dynamic processes of the interaction of atmospheric layers. Zonal wind data by 5° latitude from the website https://psn.noaa.gov at the longitudes of Europe and North America from 15 altitude levels (from 1000 to 10 hPa) and SA data from the website https://www-app3.gfz-potsdam.de were used. Twenty high-amplitude 27-day SA cycles during the decline phase of the 23rd 11-year solar cycle from 2002 to 2004 were studied. The average 27-day wind changes for each latitude and altitude are calculated by the superposed epoch analysis separately for the winter and summer seasons. For the first time, 27-day latitudinal and altitudinal variations of zonal wind with an amplitude of ~8 m/s, capable of influencing the weather in the extratropical atmosphere, were established. Despite the significant difference in the background wind field in winter and summer, the response of the wind field to SA influence is similar for both seasons. The maximum wind changes occur in the southern part of the polar atmospheric cell and the northern part of the Ferrell cell (50°–70° N) and gradually decrease in magnitude to the south and north. Wind changes are many times smaller in the tropical troposphere. At the boundaries of the global circulation cells, the direction of disturbed wind changes to the opposite. Changes in the position of jet streams by more than 1° in latitude and changes in the size of atmospheric circulation cells are also observed. In terms of height, the largest changes in the wind at all latitudes occur in the upper troposphere. There is a close relationship between the magnitude of the perturbed wind and changes in the tropopause height. The impact is realized through two-way dynamic stratospheric-tropospheric interaction, primarily in the area of the polar night jet and polar front jet stream. The presence of significant wind changes for the summer season indicates an important role not only of planetary-scale Rossby waves but also of shorter-wavelength waves. At the same time, their upward propagation can be ensured by nonlinear interaction between them.

The relevance of this study stems from the fact that, to date, there is no reliable and detailed explanation of the electromagnetic mechanism governing interactions between subsystems within the Earth (inner shells)–atmosphere–ionosphere–magnetosphere (EAIM) system. This mechanism can manifest itself under the action of high-energy sources of both natural and anthropogenic origins. Natural sources include weather fronts, thunderstorms, hurricanes (typhoons), volcanic eruptions, earthquakes, etc. All these natural processes may generate intense electromagnetic radiation in the VLF range (3–30 kHz). Such radiation is capable of interacting with the plasma in the lower ionosphere, triggering a series of secondary geophysical processes. This study presents the findings on the electromagnetic mechanism of subsystem interactions within the EAIM system, specifically focusing on the impact of intense electromagnetic radiation on the parameters of the lower ionosphere. A single lightning strike during the daytime can increase electron temperature by a factor of 60–44 at altitudes of 60–80 km, respectively. At night, a significant increase in electron temperature (by a factor of 60–50) can occur at altitudes of 80–95 km, respectively. This substantial electron heating results in the transparentization effect of the lower ionosphere plasma, leading to reduced electromagnetic radiation absorption at altitudes up to 80 km during the day. At night, however, the plasma exhibits a saturation effect at altitudes of 80–100 km, which is accompanied by an increase in electromagnetic radiation absorption. A single lightning strike does not cause a noticeable disturbance in electron density or the intensity of its fluctuations. However, it can produce minor (~0.01 nT) perturbations in the geomagnetic field and significant (~1 V/m) spikes in the vortex electric field. At a sufficiently high lightning frequency, noticeable disturbances in electron density and the intensity of its fluctuations may occur, potentially leading to the accumulation of disturbances N and (overline {Delta {{N}^{2}}} ). Significant perturbations in the parameters of the lower ionosphere can, in turn, generate secondary effects that propagate into the magnetosphere and magnetically conjugate regions.

Direct magnetic field measurements in sunspots by many spectral lines are important for elucidating the true magnitude and structure of the magnetic field at different levels of the solar atmosphere. Currently, magnetographic measurements are the most widespread, but such measurements mainly represent the longitudinal component of the magnetic field. In the sunspot umbra, such measurements give unreliable information and do not allow for determining the actual value of the module (absolute value) of the magnetic field. Such data can be obtained from spectral-polarization observations, thanks to which the magnetic field can be determined directly from Zeeman splitting, rather than as calibrated polarization in line profiles. The presented work presents the results of the study into the magnetic field in the sunspot on July 17, 2023, which was observed on the Echelle spectrograph of the horizontal solar telescope of the Astronomical Observatory of Taras Shevchenko National University of Kyiv. The I ± V profiles of ten photospheric lines of Fe I, Fe II, Ti I, and Ti II were analyzed in detail. The strongest magnetic field measured by the Fe I lines reaches 2600 G, and the difference in the measured intensities by these lines is sometimes at the level of 50–80%. The umbral lines of Ti I show, in general, the same magnetic fields as Fe I lines, while the lines of Fe II and Ti II show significantly weaker fields. Although the lateral field profile in the spot by most of the Fe I lines is smooth, quasi-Gaussian, one of the lines, namely Fe I λ 629.10 nm, shows a “dip” at 400–600 G in the sunspot umbra, which, most likely, is real. The obtained data probably indicate a combination of at least two effects: the dependence of measurements on the height of line formation in the solar atmosphere and the manifestation of Zeeman “saturation” in lines with different Lande factors. It also turned out that the umbral line of Ti I λ 630.38 nm shows somewhat stronger magnetic fields compared to non-umbral lines. The obtained data are planned to be used to clarify the general picture of the magnetic field in the spot by means of simulation.

Magnetic storm, ionospheric storm, atmospheric storm, and electrical storm are the components of a geospace storm resulting from a solar storm. In the literature, the main attention is paid to the analysis of severe and extreme geospace storms. It is these storms that have the greatest impact on the Earth–atmosphere–ionosphere–magnetosphere system. They are most dangerous for space-based and ground-based technological systems. Such storms have a significant impact on human well-being and health. Minor and moderate storms are much less studied than severe and extreme ones. There are good reasons to believe that such storms can have some impact on the systems and people. It is important that the frequency of occurrence of moderate storms is much greater than the frequency of occurrence of severe storms. All this determined the relevance of this work, which consists in the study of magnetic disturbances that arise during moderate geospace storms, which receive undeservedly little attention. The purpose of this paper is to analyze on a global scale the temporal variations of geomagnetic field components during moderate magnetic storms on April 28–29 and May 1–2, 2023. The latitudinal dependence of the geomagnetic field components temporal variations during two moderate magnetic storms in April–May 2023 and on reference days was analyzed on a global scale using the data of the global network of Intermagnet stations. The limits of fluctuations in the level of the geomagnetic field under quiet conditions and during moderate storms were estimated. The range of variations in the geomagnetic field level under quiet conditions decreased from 200–260 to 30–50 nT with decreasing geographic latitude. During the storms, these limits increased 1.3–2.1 times. The variations in the level of components at stations equidistant from the equator were close. This is true for both the Western and Eastern Hemispheres. The fluctuations of the geomagnetic field level at the stations operating approximately at the same latitude but in different hemispheres were also close.

Based on observations conducted at the Ernest Gurtovenko Horizontal Solar Telescope, the height of the polar chromosphere of the Sun was determined for the period 2012–2023. The measurement was calculated as the difference between the positions of the maximum radial brightness gradients in the continuum and at the core of the H_α line. The results indicate that the height of the polar chromosphere is lower near the maximum of the solar cycle (approximately 4500 km, or 6.3″) and higher near the minimum of the cycle (approximately 5000 km, or 6.9″). The chromosphere’s height at the southern pole in 2012–2013 and, particularly, 2016–2017 was higher than at the northern pole. This north–south asymmetry is likely related to differences in the dynamics and magnitude of the polar magnetic fields during Solar Cycle 24. The findings demonstrate that the time changes in the chromosphere’s height closely correlate with sunspot numbers, the strength of the polar magnetic field, and chromospheric indices of solar activity. The correlation coefficient between the average annual height of the chromosphere and the smoothed relative sunspot number is –0.64 for the northern hemisphere and –0.75 for the southern hemisphere. The correlation coefficient between the average annual height of the chromosphere and the smoothed values of the polar magnetic field strength (based on data from the Wilcox Solar Observatory) is 0.86 for the northern hemisphere and 0.53 for the southern hemisphere (the latter value increases to 0.77). The correlation coefficient between the average annual height of the chromosphere and the chromospheric index I_K2 reaches the highest values, 0.91, for the northern pole and 0.80 for the southern pole.