Bolotnova R.Kh., Korobchinskaya V.A. «Formation of supersonic steam-water jets accompanied by generation of acoustic pulsations» Научно-технические ведомости Санкт-Петербургского государственного политехнического университета. Физико-математические науки, 16, № S1.2, с. 330-336 (2023)

The features of supersonic steam-water jets formation under outflow through a thin nozzle from a high-pressure chamber are considered. The modes of emerging vibration processes are investigated, depending on variation of initial saturation states determined by pressure and temperature. The proposed model equations system of steam-water mixture in three-dimensional formulation, in two-temperature, single-pressure, single-velocity approximations, takes into account interphase heat exchange, evaporation and condensation phenomena. The numerical implementation of this problem is carried out by the authors developed solver in the OpenFOAM package. The process of evolution a supersonic jet with formation Mach disk is studied and the causes of generation a pressure acoustic pulsations are investigated. The analysis of influence of initial saturation states of vapor-water fluid located in a high-pressure chamber on intensity and frequency of acoustic vibrations is given. To justify the reliability numerical method in the OpenFOAM package, the obtained solution with experimental photograph of supersonic nitrogen jet owing through cylindrical nozzle from a high-pressure chamber is compared.

Uvarov Yu.A., Bykov A.M. «Asymmetry study of the mixed-morphology supernova remnant G 18.95-1.1» Научно-технические ведомости Санкт-Петербургского государственного политехнического университета. Физико-математические науки, 16, № S1.2, с. 362-369 (2023)

Radio and X-ray maps of supernova remnants (SNRs) in many cases revealed an asymmetric global structure. This may reflect the inhomogeneity of the circumstellar/ambient matter, anisotropic energy release or both. Given a growing sample of the observed SNRs some techniques to characterize the global asymmetry are needed to identify old SNRs in sky surveys among other observed extended structures of low surface brightness. We discuss here the applications of modified power-ratio technique to quantify the global asymmetry of the mixed-morphology SNR G 18.95-1.1 using its recent mapping with SRG and compare results with the well-studied SNRs IC 443 and Cas A.

Tanashkin A.S., Karpova A.V., Shibanov Yu.A., Potekhin A.Yu., Zyuzin D.A. «Middle-aged gamma-ray pulsar J0554+3107 in X-rays» Научно-технические ведомости Санкт-Петербургского государственного политехнического университета. Физико-математические науки, 16, № S1.2, с. 370-376 (2023)

We present some results of X-ray observations of the middle-aged γ-ray pulsar J0554+3107 with XMM-Newton. For the first time, we detected X-ray pulsations with the J0554+3107 spin period from the presumed X-ray counterpart, thus confirming its pulsar nature. The pulsed fraction in the 0.2–2 keV band is 25±6%. The pulsar spectrum can be fitted by the model consisting of thermal and non-thermal components. To describe the former, we created and applied hydrogen atmosphere models for neutron stars with dipole magnetic fields. In addition, an absorption feature at 0.34 keV is required to fit the spectrum. The spectral analysis implies that J0554+3107 has the effective temperature of ∼47±2 eV. The analysis also indicates that J0554+3107 may be a rather heavy neutron star with the mass of ∼1.9±0.2 M_⊙. Implementing the relation between the interstellar absorption and the distance in the pulsar direction, we obtained the distance to the pulsar to be about 2 kpc. Implications of the results for cooling scenarios of neutron stars and the equation of state of supra-dense matter in their cores are briefly discussed.

Lukyantsev D.S., Afanasiev N.T., Tanaev A.B. «Mathematical modeling of effects of plasma and gravitational inhomogeneities in the structure of electromagnetic signals» Научно-технические ведомости Санкт-Петербургского государственного политехнического университета. Физико-математические науки, 16, № S1.2, с. 377-382 (2023)

The three-dimensional algorithm of calculation of the trajectory characteristics of electromagnetic signals in a random-inhomogeneous space plasma placed in the gravity field of difficult configuration has been suggested. The influence of the gravity on the signal propagation has been taken into account by the use of efficient index of refraction. The inhomogeneities of plasma have been defined by the model of spatial correlation function of fluctuations of index of refraction. Results of mathematical modeling of lensing of electromagnetic signals in the gravity field from several space objects have been provided. It is shown that, a significantly different spatial structure of ray field can occur in picture plane of the observer depending on the properties of the gravitational field and parameters of random plasma inhomogeneities.

Chudaev S.O., Afanasiev N.T., Lukyantsev D.S. «Diagnostics of CME cavity using data of multiwave measurements of behind-the-limb solar radio bursts» Научно-технические ведомости Санкт-Петербургского государственного политехнического университета. Физико-математические науки, 16, № S1.2, с. 383-388 (2023)

Mathematical modeling of the behind-the-limb radio bursts propagation characteristics at the second harmonic of the local plasma frequency of the solar corona was performed for analytical models of the electron density of the circumsolar plasma and CMEs. The features of the bursts trajectories are studied depending on the parameters of the CMEs and the initial coordinates of solar radio sources. The conditions for the strong effect of CME on radio bursts are determined. The possibility of determining the CME cavity’s parameters from the data of multiwave measurements of the group delays of behind-the-limb radio bursts is shown.

Ivanova A.L., Astapov I.I., Bezyazeekov P.A., Bonvech E.A., Borodin A.N., Budnev N.M., Bulan A.V., Chernov D.V., Chiavassa A., Dyachok A.N., Gafarov A.R., Garmash A.Yu., Grenebyuk V.M., Gres E.O., Gres O.A., Gres T.I., Grinyuk A.A., Grishin O.G., Ivanova A.D., Ilushin M.A., Kalmykov N.N., Kindin V.V., Kiryukhin S.N., Kokoulin R.P., Kompaniets K.G., Korosteleva E.E., Kozhin V.A., Kravchenko E.A., Kryukov A.P., Kuzmichev L.A., Lagutin A.A., Lavrova M.V., Lemeshev YU.E., Lubsandorzhiev B.K., Lubsandorzhiev N.B., Malakhov S.D., Mirgazov R.R., Monkhoev R.D., Okuneva E.A., Osipova E.A., PakhorukoV A.L., Pankov L.V., Pan A., Panov A.D., Petrukhin A.A., Podgrudkov D.A., Popova E.G., Postnikov E.G., Prosin V.V., Ptuskin V.S., Pushnin A.A., Raikin R.I., Razumov A.YU., Rubtsov G.I., RYABOV E.V., Samoliga V.S., Satyshev I., Sidorenkov A.YU., Silaev A.A., Silaev A.A., Tarashchansky B.A., Tkachev L.G., Tanaev A.B., Ternovoy M.YU., Ushakov N.A., Volchugov P.A., Volkov N.V., Voronin D.M., Zagorodnikov A.V., Zhurov D.P., Yashin I.I., Vaidyanathan A. «Technique for reconstructing the parameters of eas and primary cosmic rays based on experimental data of the Tunka-Grande scintillation array» Научно-технические ведомости Санкт-Петербургского государственного политехнического университета. Физико-математические науки, 16, № S1.2, с. 389-394 (2023)

The Tunka-Grande scintillation array is a part of a single TAIGA experimental complex located in the Tunka Valley, 50 km from the Lake Baikal. It consists of 19 observation stations deployed on an area of about 0.5 km². The main aim of the Tunka-Grande facility is a detailed study of the energy spectrum and mass composition of cosmic rays in the energy range from 10 PeV to 1 EeV by detecting the charged and muon component of EAS. The article presents a method for reconstructing the parameters of the EAS and primary cosmic rays, the cosmic rays energy spectrum based on 4 measurement seasons, and compares the results obtained with the data of the Tunka-133 and TAIGA-HiSCORE Cherenkov arrays.

Khrapov S.S., Khoperskov A.V., Zaitseva N.A., Zasov A.V., Titov A.V. «Formation of spiral dwarf galaxies: observational data and results of numerical simulation» Научно-технические ведомости Санкт-Петербургского государственного политехнического университета. Физико-математические науки, 16, № S1.2, с. 395-402 (2023)

Recent studies show the possibility of the formation of fairly regular and global spiral patterns in dwarf galaxies (dS type). Our sample of observed dwarf objects of this class also includes galaxies with a central stellar bar. The analysis of the observational data provides a small rotation velocity and a small disk component mass for dS galaxies, which is in poor agreement with the spiral structure generation mechanism in isolated dwarfs due to the development of disk gravitational instability. Numerical simulation of the stellar-gaseous disks self-consistent dynamics imposes restrictions on the stellar disk thickness and the maximum gas rotation velocity, at which the gravitational mechanism of spiral formation can still be effective.

Martyusheva A.A., Devyatkin A.V., L'vov V.N. «Gravitational and non-gravitational effects in the orbital motion of asteroid 2022 AE1» Научно-технические ведомости Санкт-Петербургского государственного политехнического университета. Физико-математические науки, 16, № S1.2, с. 403-409 (2023)

Asteroid 2022 AE1 with a diameter of about 70 m, discovered at the very beginning of 2022, approached the Earth on December 31, 2021 at a minimum distance of 0.0664 au. The potential hazard of a collision with the Earth during the next close approach in 2023 was estimated by astronomers at 1 in 1700, which raised widespread public concern. Subsequent observations made it possible to refine the asteroid’s orbit and showed that the collision will be avoided. However, the upcoming close encounters of this asteroid with the Earth and, especially, with Venus, as well as possible approaches with the main belt asteroids, require not to weaken the attention to this object. Gravitational and non-gravitational effects can have a significant impact on its orbit and, as a consequence, lead to a collision with one of the inner planets. In this work, the displacements of asteroid 2022 AE1 under the influence of solar radiation pressure were calculated over several time intervals for various values of the average density of the object. Furthermore, the diurnal and seasonal components of the Yarkovsky effect were calculated for various rotation periods and axial tilt angles of the asteroid. As a result of the simulation, possible orbits of the asteroid were obtained and a probability estimation of the asteroid collision with the Earth was made.

Bodganov A.A., Repman G.A., Tuboltsev Yu.V., Chichagov Yu.V., Kholupenko E.E., Krasilchtchikov A.M. «Development of detector cluster based on silicon photomultipliers for the Cherenkov gamma-ray telescope TAIGA-IACT» Научно-технические ведомости Санкт-Петербургского государственного политехнического университета. Физико-математические науки, 16, № S1.2, с. 410-416 (2023)

A new experimental detector cluster for the TAIGA-IACT telescope has been developed. The cluster contains 28 pixels based on MicroFJ-60035 silicon photomultipliers, whose signal is digitized with an analog memory chip (switched capacitor array) DRS4 at a frequency of up to 5 GHz. The paper describes the device and the operation principles of the detector cluster, reveals the peculiarities encountered in the development process. Dark chamber tests of the cluster with a point source of short pulses of ultraviolet light have allowed us to obtain dependencies of the cluster conversion coefficient and the maximum value of the recorded signal on the overvoltage of the silicon detectors.

Antonov A.S., Bodganov A.A., Krasilchtchikov A.M. «Design of an optical concentrators array for the camera of a small-size Cherenkov gamma-ray telescope» Научно-технические ведомости Санкт-Петербургского государственного политехнического университета. Физико-математические науки, 16, № S1.2, с. 417-422 (2023)

Quantitative modeling of a system of optical concentrators based on an improved design of Winston hexagonal cones, providing a possibility of using light filters and intended for the registration camera of a small-size Cherenkov gamma-ray telescope, has been performed. The transmission of the cones is calculated, and the intensity distributions of the photon flux in the detector plane are given. Based on the results obtained, an optimal configuration of optical concentrators is proposed with an account for design features of the TAIGA-IACT mount, mirror, and camera, as well as of new detector units. The results obtained for the considered system are compared with the previously published models.

Krasilchtchikov A.M., Kholupenko E.E., Badmaev D.V., Bodganov A.A. «Modeling of performance enhancement of the TAIGA-IACT Cherenkov gamma-ray telescope equipped with semiconductor photomultipliers» Научно-технические ведомости Санкт-Петербургского государственного политехнического университета. Физико-математические науки, 16, № S1.2, с. 423-428 (2023)

We present modeling of effective area and count rates of a TAIGA-IACT Cherenkov gamma-ray telescope unit with an upgraded camera based on semiconductor photo detectors (SiPM) OnSemi MicroFJ-60035 and optical filters SL 290-590 and SL 280-390. In comparison with the current configuration of TAIGA-IACT where classic vacuum photomultipliers are employed, the threshold detection energy of cosmic gamma-quanta by a TAIGA-IACT unit equipped with a SIiPM-based camera and a wide-band optical filter SL 290590 would be reduced down to about 0.4 TeV, and with a narrower filter SL 280–390 down to about 0.7 TeV. Application of semiconductor photo detectors, which are stable against excess illumination, and optical filters of the near-UV band allows one to substantially increase the duty cycle of a Cherenkov gamma-ray telescopes due to the possibility to carry out observations during moonlit nights and at twilight even without a need to substantially increase the trigger threshold. Hence, one may conclude that a TAIGA-IACT unit with an upgraded camera with SiPM detectors will be an efficient instrument for studies of TeV-range emission from space gamma-ray objects.

Popov A.N., Barsukov D.P., Ivanchik A.V., Bobashev S.V. «Positron production due to interaction of cosmological background photons» Научно-технические ведомости Санкт-Петербургского государственного политехнического университета. Физико-математические науки, 16, № S1.2, с. 429-435 (2023)

The interaction of photons of the cosmological background radiation with producing electron-positron pairs is considered. It is shown that main input in positron production is given by interaction of cosmological gamma-ray background photons with photons of extragalactic background light, although taking into account the interaction of cosmological gamma-ray background photons with cosmological ultraviolet background photons may substantially increase the pair production rate.

Kosenko D.N., Balashev S.A. «HD molecules in the Magellanic Clouds» Научно-технические ведомости Санкт-Петербургского государственного политехнического университета. Физико-математические науки, 16, № S1.2, с. 436-441 (2023)

We present the detection of HD absorption lines in the Magellanic Clouds using FUSE space telescope archival data. We found HD in five (including one known) absorption systems in the Large Magellanic Cloud and three systems in the Small Magellanic Cloud. The measured HD column densities, N(HD), vary from 2·10¹³ to 2·10¹⁵ cm^–2 for associated H2 column densities, NH₂, in the range 3·10¹⁹ to 5·10²⁰ cm^–2. Using Hubble Space Telescope archival data, we also determined the population of CI fine-structure levels and metallicities in these systems. The modelling of obtained observational data for HD, H2 and C I allow us to estimate physical conditions in the interstellar medium of the Magellanic Clouds associated with these absorption systems, namely, the cosmic ray ionization rate, ultraviolet field intensity and number density.

Kuznetsov V.I., Bakaleinikov L.A., Flegontova E.Yu. «Stability of steady states of plasma diodes with counter-streaming electron and positron flows» Научно-технические ведомости Санкт-Петербургского государственного политехнического университета. Физико-математические науки, 16, № S1.2, с. 442-448 (2023)

Stability of steady states of a planar geometry diode with counter flows of electrons and positrons is studied. The study is related to the elucidation of pulsar RF radiation nature. The equation for the electric field perturbation is derived. Its exact solution is obtained for the case of a homogeneous steady-state field. The study of the dispersion equation obtained has shown that there is a threshold for the inter-electrode gap value, above which steady-state solutions are unstable. The instability threshold turned out to be √2 times higher than the known Pierce threshold.

Petrova S.N., Devyatkin A.V., L'vov V.N. «The Earth trojans» Научно-технические ведомости Санкт-Петербургского государственного политехнического университета. Физико-математические науки, 16, № S1.2, с. 449-453 (2023)

Asteroids 2010 TK7 and 2020 XL5 are of particular interest because of their behavior, which is similar to the so-called trojan asteroids. In this paper, computer simulations of the orbital evolution of the asteroids in question were carried out using the EPOS software system. The results of the computer simulations suggest that the Earth trojans were not ordinary trojans in the recent past and will most likely shift to another type of orbit in the distant future.

Veretenenko S.V., Dmitriev P.B., Dergachev V.A. «Long-term effects of solar activity on cyclone tracks in the North Atlantic» Научно-технические ведомости Санкт-Петербургского государственного политехнического университета. Физико-математические науки, 16, № S1.2, с. 454-460 (2023)

Long-term changes of extratropical cyclone trajectories in the North Atlantic in cold months (October-March) were analyzed, with the data of Mean Sea Level Pressure archives from Climatic Research Unit, UK (1873–2000) and NCEP/DOE AMIP-II Reanalysis (1979–2021) being used. It was revealed that variations of latitudes of storm tracks in the longitudinal range from 60°W to 10°W are characterized by pronounced periodicities of ∼80–90 and ∼22 years. This indicates their possible relation to the corresponding periodicities in solar/geomagnetic activity and galactic cosmic ray variations, the secular Gleissberg cycle and the magnetic Hale cycle, respectively. At the maximum of the secular cycle, trajectories of North Atlantic cyclones were found to shift a few degrees south, whereas at the minimum and the descending phase they shift to the north. As North Atlantic cyclones influence significantly weather and climate conditions over Europe, oscillations of their tracks associated with solar activity and related phenomena seem to be of great prognostic importance.

Romansky V.I., Bykov A.M., Osipov S.M. «Kinetic modeling of MHD parameters of mildly-relativistic shocks» Научно-технические ведомости Санкт-Петербургского государственного политехнического университета. Физико-математические науки, 16, № S1.2, с. 461-466 (2023)

Mildly-relativistic outflows with shocks of velocities 0.1–0.7c were deduced from multiwavelength observations of powerful fast transient sources. These outflows are associated with merging relativistic objects, relativistic supernovae and fast blue optical transients. Relativistic magneto-hydrodynamic (RMHD) models of these objects rely on the equation of state of the fluid, which is a collisionless plasma with a contribution of non-thermal components. In this paper, we present kinetic simulations of mildly-relativistic shocks with Particle-in-Cell and Monte-Carlo techniques to derive the adiabatic index of plasma in the shock downstream directly from the particle distributions, which can be implemented into the RMHD models.

Dranevich V.A., Dmitriev P.B. «Dynamics of quasi-periodic oscillations in the light curve of the GRB 190114C γ-ray burst» Научно-технические ведомости Санкт-Петербургского государственного политехнического университета. Физико-математические науки, 16, № S1.2, с. 467-473 (2023)

Based on the γ-ray Burst Monitor data of the Fermi space observatory, the light curve time structure of the γ-ray burst GRB 190114C in the energy range from 5 keV to 50 MeV was investigated. It was found that the temporal structure of the emission of this γ-ray burst contains quasi-periodic components with periods of 0.768 s, 1.28 s, 2.24 s, and 3.84 s, determined with an accuracy of up to ±0.064 s where the original data time bin is 0.064 s. We also analyzed the evolution of these quasi-period values during the background radiation intensity, which was recorded within 137 s before and within 354 s after the event. As a result, a systematic decrease with time in the value of the quasi-period of 3.84 s was found, while the value of the quasi-period of 0.768 s at the same time gradually increases. A similar unambiguous result for the quasi-periods of 1.28 s and 2.24 s was not obtained. According to the above estimates, it should be noted that the γ-ray burst itself is located within the time interval when oscillations with quasi-periods of 2.24 s and 3.84 s are in a multiple ratio of ∼3/5. Such coincidence can serve as an indication of the significant role of resonance phenomena in the process of formation and flow of a γ-ray burst.

Ridnaia A.V., Frederiks D.D., Svinkin D.S., Lysenko A.L., Tsvetkova A.E., Ulanov M.V. «Search for gamma-ray counterparts to FRBs in Konus-Wind data» Научно-технические ведомости Санкт-Петербургского государственного политехнического университета. Физико-математические науки, 16, № S1.2, с. 474-479 (2023)

We report preliminary results of the search in the Konus-Wind experiment data for hard X-ray/soft γ-ray emission in coincidence with publicly reported fast radio bursts (FRBs). We find no significant associations for any of the 581 FRBs in our sample and report upper limits to the high-energy fluence/peak flux for three spectral shapes, which generally describe short GRB, long GRB and magnetar giant flare spectra. In addition to study each individual FRB, we perform a stacking analysis of the bursts from each repeating source in our sample and a separate stacking analysis of the bursts from the non-repeating FRBs. We find no statistically significant excess of the cumulative emission over background level for either case.

Monkhoev R.D., Astapov I.I., Bezyazeekov P.A., Bonvech E.A., Borodin A.N., Budnev N.M., Bulan A.V., Vaidyanathan A., Volkov N.V., Volchugov P.A., Voronin D.M., Gafarov A.R., Gres E.O., Gress O.A., Gress T.I., Grishin O.G., Garmash A.Y., Grebenyuk V.M., Grinyuk A.A., Dyachok A.N., Zhurov D.P., Zagorodnikov A.V., Ivanova A.D., Ivanova A.L., Iliushin M.A., Kalmykov N.N., Kindin V.V., Kiryukhin S.N., Kokoulin R.P., Kolosov N.I., Konstantin G.C., Korosteleva E.E., Kozhin V.A., Kravchenko E.A., Kryukov A.P., Kuzmichev L.A., Chiavassa A., Lagutin A.A., Lavrova M.V., Lemeshev Y.E., Lubsandorzhiev B.K., Lubsandorzhiev N.B., Malakhov S.D., Mirgazov R.R., Okuneva E.A., Osipova E.A., Pakhorukov A.L., Pan A., Panov A.D., Pankov L.V., Petrukhin A.A., PodgrudkoV D.A., Popova E.G., Postnikov E.B., Prosin V.V., Ptuskin V.S., Pushnin A.A., Razumov A.Y., Raikin R.I., Rubtsov G.I., Ryabov E.V., Samoliga V.S., Satyshev I., Silaev A.A., Silaev A.A., Sidorenkov A.Y., Skurikhin A.V., Sokolov A.V., Sveshnikova L.G., Tabolenko V.A., Tanaev A.B., Tarashchansky B.A., Ternovoy M.Y., Tkachev L.G., Ushakov N.A., Chernov D.V., Yashin I.I «Method for gamma-hadron separation according to the experimental data of the Tunka-Grande array» Научно-технические ведомости Санкт-Петербургского государственного политехнического университета. Физико-математические науки, 16, № S1.2, с. 480-484 (2023)

The Tunka-Grande array is a part of unified experimental complex, which also includes Tunka-133 and TAIGA-HiSCORE (High Sensitivity COsmic Rays and gamma Explorer) wide-angle Cherenkov arrays, TAIGA-IACT array (Imaging Atmospheric Cherenkov Telescope) and TAIGA-Muon scintillation array. This complex is located in the Tunka Valley (Buryatia Republic, Russia), 50 km from Lake Baikal. It is designed to study the energy spectrum and the mass composition of charged cosmic rays in the energy range 100 TeV-1000 PeV, to search for diffuse gamma rays above 100 TeV and to study local sources of gamma rays with energies above 30 TeV. This report outlines 3 key points. The first is the description of the Tunka-Grande scintillation array. The second one presents the strategy of the search for diffuse gamma rays based on a computer simulation of the Tunka-Grande array. The third one is devoted to the prospects for future research in the field of gamma-ray astronomy using simulation results.

Shabalin A.N., Charikov Yu.E. «Electron acceleration in models with a vertical current sheet» Научно-технические ведомости Санкт-Петербургского государственного политехнического университета. Физико-математические науки, 16, № S1.2, с. 485-491 (2023)

Model of solar flares with a vertical current sheet and a cusp above the magnetic arcade is considered. In some flares, such magnetic field geometry can be observed directly in the extreme ultraviolet range. According to the model, the relaxation of helmet-like magnetic loops formed due to magnetic field reconnection is supposed. During the relaxation, the magnetic field and the loop length vary with time. Consequently, a betatron acceleration and first-order Fermi electron acceleration appeared. In a kinetic approach the time-dependent kinetic equation for the distribution function of initially accelerated electrons is numerically solved. It is shown that because of such acceleration, the electron energy spectra changes significantly. The proportion of high-energy electrons with energies of more than 200 keV increases by 1–3 orders of magnitude depending on the pitch-angular distribution of accelerated electrons formed in the primary accelerator – the current sheet.

Ovchinnikova E.P. «X-ray radiation of partially occulted solar flare of May 13, 2013» Научно-технические ведомости Санкт-Петербургского государственного политехнического университета. Физико-математические науки, 16, № S1.2, с. 492-498 (2023)

The X-ray emission of the SOL2013-05-13T02:12 X1.7-GOES-class flare registered by the RHESSI spectrometer was analyzed. Various models of fitting the X-ray spectrum are applied. The following radiation models are considered: a two-temperature hot plasma model, a combination of a thin target model and a single-temperature plasma model, a combination of a bremsstrahlung model of a thick target and quasi-thermal radiation of a single-temperature plasma. Their validity to the spectra for this event is discussed. Plasma parameters are evaluated: emission measures, temperatures and density.

Balashev S.A., Kosenko D.N. «Neutral carbon in the diffuse cold neutral medium» Научно-технические ведомости Санкт-Петербургского государственного политехнического университета. Физико-математические науки, 16, № S1.2, с. 499-504 (2023)

We discuss the relative abundance of C I/H2 in the diffuse cold neutral medium. Using semi-analytical formalism, we describe how C I/H2 depends on the main parameters of the medium: number density, metallicity, strength of the UV field and cosmic ray ionization rate. We show that observed relative abundance of C I/H2 in the high-redshift damped Lyman alpha systems can be reproduced within our model assuming the typical expected conditions in the diffuse cold medium. We also discuss that the observed relative abundance of C I/H2, when coupled with data on the population of the fine structure levels of neutral carbon and the rotational levels of molecular hydrogen can be used to derive the cosmic ray ionization rate in the low-metallicity interstellar medium.

Trofimov D.A., Petrov S.D., Kalishin A.S., Lukin V.V., Serov Yu.A., Chekunov I.V. «Structure and variations of the south-polar ionosphere by GNSS- tomography» Научно-технические ведомости Санкт-Петербургского государственного политехнического университета. Физико-математические науки, 16, № S1.2, с. 505-510 (2023)

The paper is devoted to determination of the total electron content in the vicinity of the South geomagnetic pole using observations by global navigation satellite systems. Observations were carried out at the Russian Antarctic station Vostok in the periods February 2016 – January 2017, February 2018 – February 2019 and February 2020 – January 2021. Observations were made with satellites of GPS and GLONASS systems. Processing of observations was carried out by use of the TEC-suite software. Total electron content series were obtained for the specified time periods. Our results were compared with those of Center for Orbit Determination in Europe, there is a good agreement, based on which we conclude that our data are reliable. For all periods of observation, average daily profiles of changes in the total electron content in winter and summer were plotted. An excess of the winter total electron content measured from global navigation satellite systems observations over the model data provided by Center for Orbit Determination in Europe by about 5 total electron content unit was noted.

Andreev A.O., Nefedyev Yu.A., Demina N.Yu., Kolosov Yu.A., Korchagina E.P. «Multiparametric analysis of celestial bodies as sources of space resources» Научно-технические ведомости Санкт-Петербургского государственного политехнического университета. Физико-математические науки, 16, № S1.2, с. 511-516 (2023)

The work is devoted to the creation of a method based on data from space missions such as LRO (Lunar Reconnaissance Orbiter) and the analysis of possible impactors and meteoroid material for mapping the distribution of minerals on the Moon. In the process of surveys from the Lunar Reconnaissance Orbiter (LRO) spacecraft, the most recent generalized information on the distribution of iron and titanium in the composition of the lunar surface rocks was obtained. To obtain these data, it was necessary to compile a single map from more than 4 thousand images that the LRO spacecraft took during a month of work in a lunar orbit. The processing of the obtained data made it possible to detect areas on the lunar surface containing significant deposits of titanium. The results were calibrated using analyzes of lunar soil samples brought to Earth by the American Apollo missions and Soviet automatic vehicles of the Luna series. Concrete results obtained: Map of mineral distribution gradients depending on selenographic coordinates on the lunar sphere.

Zagidullin A.A., Petrova N.K., Nefedyev Yu.A., Andreev A.O. «Creation of a generalized dynamic model of planetary moons based on an analytical approach for describing the libration processes of their rotation» Научно-технические ведомости Санкт-Петербургского государственного политехнического университета. Физико-математические науки, 16, № S1.2, с. 517-522 (2023)

Our work is devoted to the creation of a generalized dynamic model that describes libration processes in the motion of the natural satellite of the planet, which has been tested on the simulation of the moons rotational parameters(MRPs) of the Earth’s Moon and allows adapting description system of MRPs to other celestial objects, having a librational nature of rotation as well. In this case, it is assumed that an analytical approach was used to describe the rotational motion, which, on the one hand, is rather complicated for solving the equations of rotation and has a lower accuracy than the numerical one, but, on the other hand, the resulting analytical representation of MRPs provides a more convenient tool for analyzing the behavior of MRPs with changes in various parameters, determining the rotational dynamics of the satellite.It is with its help that the procedure of flexible computer simulation of the rotation process and the identification of those observational manifestations, which are determined primarily by the parameters of the figure of a celestial body – the laws of distribution of body mass, compression, non-sphericity.

Sergienko M.V., Sokolova M.G., Nefedyev Yu.A., Andreev A.O. «ρ-Geminids meteor shower and its connection with near-earth asteroids» Научно-технические ведомости Санкт-Петербургского государственного политехнического университета. Физико-математические науки, 16, № S1.2, с. 523-529 (2023)

In this work, genetic connections (GC) of the small meteor shower ρ-Geminids with near-Earth objects (NEOs) of the Apollo group were studied using the author’s multi-parameter method. The multiparameter method for determining GC of meteor showers with probable parent bodies is based on the use of a set of criteria for identifying orbits, such as: D-criterion by Drummond, Kholshevnikov’s metric, Tisserand’s parameter, μ and ν quasi-stationary parameters of the restricted three-body problem, longitude of perihelion π of meteor orbit. The method of identifying meteoroids with asteroids involves computational procedures and the calculation of critical values for each of the criteria used, which increases the reliability of finding the GC for the objects under study. The catalogues of meteor orbits: Meteoroid Orbit Database v3.0, CAMS and EDMOND 5 v.04 of the European Meteor Network were used as source material in the work.

Churkin K.O., Andreev A.O., Nefedyev Yu.A., Kolosov Yu.A., Korchagina E.P., Demina N.Yu., Borovskih V.S. «Analysis of comet C/1969 Y1 parameters using isophote structural modeling» Научно-технические ведомости Санкт-Петербургского государственного политехнического университета. Физико-математические науки, 16, № S1.2, с. 530-535 (2023)

This work is devoted to the construction of a brightness structural model of the long-period comet Bennett C/1969 Y1. This comet belongs to the comets of the Jupiter family (JF) and has a Tisserand’s parameter T>2. Determining the brightness characteristics of the comet has been one of the most important goals of cometary observations over the past century. The complexity of such studies lies in the fact that we are dealing with extended sources moving relative to background stars. The problem of obtaining reliable estimates of the distribution of brightness parameters (BPs) for long-period comets also remains especially important, because for many of them observations were made back in the days when high-precision methods, such as CCD-matrices and other technical tools, were not available. At the same time, most of the determined stellar magnitudes of long-period comets were related to the gaseous coma surrounding the comet’s nucleus, and not to the comet’s nucleus itself. At the same time, cosmic ultraviolet observations of comets in the Lyman-alpha hydrogen lines made it possible to obtain very important data for estimating the emission of H₂O by the cometary nucleus, as well as other types of molecules (e.g. C₂, C₃, CN, OH). In the presence of dependencies between the productivity of the H₂O cometary nucleus and its brightness characteristics, the determination of BPs of cometary nuclei has acquired a new meaning. However, the dependence of the size of the nucleus on its BPs is not linear, since there is a correlation with the albedo of the surface of the nucleus. In this work, BPs and albedo for comet Bennett C/1969 Y1 are studied. Taking into account the data obtained and the solution of the described problems, we applied the author’s isophote method to analyze the structure of the brightness characteristics of Bennett C/1969 Y1.

Chukov V.N. «Structure of acoustic lauegram on the ewald circle of reflection for the rayleigh wave scattering» Научно-технические ведомости Санкт-Петербургского государственного политехнического университета. Физико-математические науки, 16, № S1.2, с. 557-564 (2023)

The acoustic Lauegram of the Rayleigh wave the Laue–Bragg–Wulff high-frequency scattering on a rectangle rough band of an isotropic solid, having periodic lattice of an arbitrary number of the roughness discontinuities, is theoretically investigated in details in dependence on the angle of scattering φs at a fixed ratio of the lattice unit cell size to the wavelength and parameters of the lattice. The Ewald conception of the circle of reflection is used. The problem of an arbitrary number, defined beforehand, of the resonances of scattering, i.e. nodes of the reciprocal lattice, for any φs, defined beforehand, lying on the Ewald circle of reflection, is first solved analytically in the present work in the classical case, i.e. without influence of the amplitude form-factor of the lattice. It is found, that increasing of the number of resonances for any φs is necessarily accompanied by the increasing of the Ewald circle of reflection radius, i.e. of the Rayleigh wave frequency, at fixed sizes of a discontinuities lattice. It is obtained first, that amplitude form-factor of the discontinuities lattice strongly influences the structure of the acoustic Lauegram: arbitrary number of the resonances of scattering for any φs can be placed on the Ewald circle of reflection without variation of its radius by using of the appropriate amplitude form-factor of a discontinuities lattice of a solid roughness.