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Abstract: To study the phenomena occurring on the Sun and in interplanetary space and their influence on near-Earth space and on processes in the outer and inner shells of the Earth, the results of continuous long-term observations of solar activity become very valuable. A representative collection of such long-term homogeneous series of systematic observations obtained by the worldwide network of solar and astronomical observatories, as well as by spacecraft, has been collected at the World Data Center for Solar–Terrestrial Physics in Moscow. The article describes a cumulative interactive catalog of the main characteristics of significant solar-flare events of the current 25th cycle of solar activity. PubDate: 2023-12-01
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Abstract: We have considered possible architecture options for an interplanetary communication system in which a data relay is used. The structure of a typical space communication link and the ways to improve its efficiency are analyzed. As one possibility, it is proposed to use accompanying orbital data-relay satellites providing the required data-transmission rate in the mode of formation flight together with the research spacecraft (SC). The optimization of the heliocentric leg of the flight trajectory of the Martian research SC and its accompanying data-relay satellite was carried out. The principal possibility of providing a formation flight of the data-relay satellite and research SC to improve communication with the Earth is demonstrated. Estimates were obtained for the masses of data-relay satellite and research SC with regard to the use of medium-lift launch vehicle of Soyuz type and a Fregat booster. Estimates are given for an increase in the duration of high-speed communication due to the use of a data-relay satellite in libration points L4 and L5 of the Earth–Sun system, as well as in heliocentric circular orbits with different radii. PubDate: 2023-12-01
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Abstract: People across the world have been fascinated by solar eclipses for thousands of years. Solar eclipses are not only fascinating to observe but also provide opportunities for scientific research. During a solar eclipse, the quantity of solar energy reaching the Earth’s surface is reduced as the Moon passes in front of the Sun. This reduction in solar energy can have an effect on the Total Electron Content of the Earth’s ionosphere. In this paper, prediction and analysis of TEC variations in the Ionosphere during the solar eclipses happened on 26.12.2019 between 04:51 to 7:34 hours (UTC) and 09.03.2016 between 12:18 to 1:02 hours (UTC) over the Indonesia region were done by using two models: Ordinary Kriging based Surrogate Model (OKSM) and Feed-Forward Neural Network (FFNN). During the eclipse period, the TEC values were predicted by the OKSM and FFNN models and it is validated using literature. For this study, the GPS data belonging to the BAKO station situated in Indonesia were collected from IONOLAB servers and the input parameters were collected from the OMNIWEB servers. Forty days prior TEC data and input parameters were used to predict the TEC values. The credibility of the predicted results is assessed using statistical factors such as RMSE, CC, MAE, MAPE, sMAPE and R-Square. The statistical results show OKSM has performed well when compared to the FFNN model over the annular and total solar eclipse period. The study suggests that combining multiple modelling methods, such as OKSM and FFNN can improve our understanding of ionospheric variability during solar eclipses and provide more accurate predictions of TEC variations. This has important implications for satellite communications and navigation systems that rely on accurate TEC measurements for positioning and timing. PubDate: 2023-12-01
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Abstract: Collisions between electrons and neutral molecules are of special interest for the physics of the Earth’s ionosphere, in particular, for determining the ionospheric conductivity and current systems in the lower ionosphere of the planet, as well as elucidating the role they play in attenuating radio waves propagating inside the D and E regions of the ionosphere. The effective collision frequency of electrons can be estimated from laboratory studies of electron mobility in atmospheric gases in combination with rocket measurements of temperature and particle density in the Earth’s upper atmosphere, or it can be determined independently from analysis of radio occultation data. We have developed a method for reconstructing the vertical profiles of the absorption coefficient of decimeter (wavelength ~19 cm) radio waves by solving the inverse problem of signal absorption in the D and E regions of the Earth’s ionosphere. Based on the analysis of radio occultation data from the FORMOSAT-3/COSMIC satellites, the altitude profiles of the absorption coefficient of decimeter (DM) radio waves in the planet’s ionosphere during the geomagnetic storm on June 22–23, 2015, were determined. It is known that the absorption coefficient at a given fixed frequency is directly proportional to both the electron density and the collision frequency of electrons with ions and neutrals. Using the data on the vertical profiles of the absorption coefficient of DM radio waves and the electron density reconstructed from the analysis of FORMOSAT-3/COSMIC radio occultations, we estimated the effective collision frequency of electrons in the D and E regions of the Earth’s high-latitude ionosphere. The practical significance of studying the frequency of electron collisions and the effects of radio wave absorption in the D and E regions of the planet’s ionosphere is associated with maintaining the uninterrupted operation of space radio communication and navigation systems. PubDate: 2023-12-01
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Abstract: The results are presented of combined measurements by the SWARM spacecraft (SC) and European incoherent scatter radar on Svalbard for two events of simultaneous observations: in the nighttime ionosphere during substorm activation on January 9, 2014, and in the daytime ionosphere under quiet conditions on February 5, 2017. Onboard magnetometers of the SWARM SC provide measurements of field-aligned current density over the ionosphere. The radar, which is under the flyby trajectory at this time, measures the vertical distribution of the electron density (Ne). Experiments have shown that, under disturbed nighttime conditions, at the location of the field-aligned current flowing from the ionosphere, the plasma density increases throughout the entire slab of the ionosphere and the change in Ne is in agreement with theoretical estimates. In the daytime quiet ionosphere, Ne increases only in the F layer, but practically does not change in the E layer. The differences may be due to the fact that, in the first case, the carriers of the upward directed current are represented by the entire energy spectrum of auroral electrons of 1–10 keV, and in the second case only by the low-energy part. PubDate: 2023-12-01
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Abstract: The influence of internal dissipation on the rotational motion of the Earth in the gravitational field of the Sun and Moon is studied within the model of M.A. Lavrentiev. The averaged equations of second approximation describing the evolution of the Earth’s rotation axis and the magnitude of its angular velocity are obtained. The dependence of the rate of evolution on the values of the model parameters is studied. Phase trajectories of the evolutionary process are constructed for different parameter values. It is shown that the observed drift of the Earth’s magnetic poles can be explained within the framework of a mechanical model by the angular acceleration of the Earth. PubDate: 2023-12-01
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Abstract: The problem of improving the neural network forecast of geomagnetic index Dst under conditions in which the input data for such a forecast are measured by two spacecraft, one of which is close to the end of its life cycle, and the data history of the other is not yet enough to construct a neural network forecast of the required quality. For an efficient transition from the data of one spacecraft to the data of another, it is necessary to use methods of domain adaptation. This paper tests and compares several data translation methods. Also, for each translated attribute, an optimal set of parameters for its translation were found, which further reduces the difference between domains. The paper shows that the use of domain adaptation methods with the selection of significant features can improve the forecast compared to the results of using untranslated data. PubDate: 2023-12-01
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Abstract: The results of information analysis of the time series of satellite monitoring of the state of the interplanetary magnetic field provided by the database of the Goddard Space Flight Center. In the arsenal of analysis methods, the main attention is paid to the control of nonextensive properties when scaling time samples created on the basis of the 2001–2022 time series. The reconstruction of the modality of the probability-distribution function for the components of the interplanetary magnetic field in the considered ensemble of realizations is demonstrated. The results of the reconstruction of the kinetics of the Shannon–Boltzmann–Gibbs, Tsallis, and Rényi entropy measures are presented. In a nonextensive approximation, the influence of q-deformation of the phase space on the stochastic regimes of the system under study. In this work, for the first time, the kinetics of information discrepancy and the kinetics of entropy measures of the ensemble of realizations of the values of the interplanetary magnetic field are studied together. The need for approval is indicated by the q-deformation parameters of the phase space, the reference and controlled subsystems, including when using asymptotic approximations in forecasting methods using neural-network algorithms and deep-learning algorithms. PubDate: 2023-12-01
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Abstract: A prototype service for MHD modeling of the calm solar wind and forecasting the speed and density of solar wind particles in interplanetary space, similar to the NOAA and ESA services, has been created. The service consists of an MHD simulator, a module for processing simulation results, and a web interface. The simulator is based on the implementation of the TVDLF method in the PLUTO package. The boundary conditions of the model (density, radial velocity, magnetic field, temperature) at a distance of 0.1 AU from the origin are obtained regularly from the corresponding NOAA service, in which they are calculated according to the WSA model based on the magnetograms of the GONG network. Two modes of boundary conditions are available: constant and daily. The simulations were carried out on a uniform grid in the range of 0.1–1.7 AU by distance (512 elements), –60°...+60° by latitude (60 elements), 0°–360° by longitude (180 elements). The calculated particle velocity and density maps are compared with the NOAA SWPC and NASA CCMC calculations under the same boundary conditions. A retrospective comparison of the resulting forecasts with data from direct measurements (OMNI) was carried out. PubDate: 2023-12-01
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Abstract: Estimates of excitation thresholds and the analysis of spectral features of narrowband stimulated electromagnetic emission (NSEE) depending on the electric-field intensity of an extraordinary polarized HF pump wave have been carried out. They are based on results obtained during power stepping EISCAT/Heating experiments. The HF pump wave was radiated toward the magnetic zenith at frequency of 5.423 MHz. The effective radiated power was changed from 55 to 360 MW. NSEE was recorded in the vicinity of St. Petersburg at a distance of ~1200 km away of the EISCAT/Heating facility. Calculations of the electric field of a powerful HF radio wave near the reflection altitude taking into account the nondeviation absorption in the underlying layers were performed. The threshold (minimum) values of the electric field required for the NSEE excitation were determined. PubDate: 2023-12-01
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Abstract: This paper considers the problem of constructing time-optimal trajectories for a spacecraft (SC) with a solar sail. The trajectories under consideration consist of repeated cycles of spacecraft movement to the target heliocentric orbit and back to the initial one. A model of a perfectly reflecting sail is used, which allows using the programs for optimal control of the sail angle, obtained on the basis of the Pontryagin maximum principle. The heliocentric motion is modeled in a flat polar coordinate system, and the spacecraft itself makes cyclic flights between two terrestrial planets along a closed trajectory. A boundary-value problem is formulated, in the solution of which the approach of the spacecraft to the target planet with the equalization of velocities is ensured (the encounter problem). Simulations of four cycles of Earth–Mercury–Earth and Earth–Mars–Earth motion with a characteristic acceleration of the solar sail of 0.25 mm/s2 have been carried out, for which the duration of one cycle is on average 2000 and 2341 days, respectively. Optimal sail-orientation control programs are obtained for a wide range of launch dates, and methods of searching for and choosing the initial values of conjugate variables are shown. The obtained results demonstrate the ability of a spacecraft with a solar sail to implement controlled motion along closed trajectories with a minimum duration of individual Earth–destination planet–Earth flights. PubDate: 2023-12-01
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Abstract: An Erratum to this paper has been published: https://doi.org/10.1134/S0010952523330031 PubDate: 2023-10-01
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Abstract: An Erratum to this paper has been published: https://doi.org/10.1134/S001095252333002X PubDate: 2023-10-01
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Abstract: An Erratum to this paper has been published: https://doi.org/10.1134/S0010952523330018 PubDate: 2023-10-01
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Abstract: The transfer scheme that provides a parabolic entry of the spacecraft into the Earth’s atmosphere has been optimized. Such a maneuver can be of interest in experimental testing of the spacecraft reentry from the Moon or after interplanetary missions. It is assumed that the spacecraft is inserted into a low Earth orbit and is equipped with a chemical propulsion system and a limited-thrust engine, which should provide a maneuver to bring the spacecraft into the Earth’s atmosphere. The optimization criterion takes into account the characteristic velocity of the maneuver. The developed method of optimizing the transfer scheme and the spacecraft trajectory itself is based on the maximum principle. Single-revolution and multi-revolution transfer trajectories are analyzed. It is shown that for single-revolution trajectories there is an optimal time and an optimal angular distance of flight. Their values and the minimum characteristic velocity of the maneuver are evaluated. Unlike single-revolution trajectories, the characteristic velocity for multi-revolution trajectories monotonically decreases with increasing transfer duration. The dependence of the characteristic velocity on the transfer duration for single-, two-, three- and four-revolution trajectories is given. The transfer duration ranges in which it is advisable to use each type of trajectory are analyzed. PubDate: 2023-10-01
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Abstract: The procedure of experimental determination of statistical characteristics of own electromagnetic radiation of a laboratory mock-up of an SPT-70 stationary plasma thruster developed by the Research Institute of Applied Mechanics and Electrodynamics of the Moscow Aviation Institute is described. The study investigated the temporal complex implementation of the processes of radiation of the SPT-70 with a sampling duration of 1 ms and an analysis band of 140 MHz for characteristic central frequencies of 0.9, 1.050, 1.200, and 1.350 GHz (discharge power of 600 W, horizontal polarization) when working on various working bodies. The conducted studies allowed to obtain estimates of the statistical characteristics of the SPT-70 radiation for prospective working bodies The new results should be attributed to the fact that the obtained distribution laws for the common-phase and quadrature components of the complex envelope process of radiation differ significantly from the Gaussian one. As for the distribution of the amplitude envelope process, in general, there is a difference from the Rayleigh distribution law. In the transition from xenon to krypton, the degree of negativity and the difference from Rayleigh’s law increase. At the same time, the law of phase distribution of the complex envelope process is close to uniform and invariant to the type of working body. PubDate: 2023-10-01
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Abstract: Possible aspects of violation of the functional safety of spacecraft in terms of electromagnetic compatibility with electric rocket thrusters in their work on alternative working substances are considered. The procedure of experimental determination of spectral–time characteristics of own electromagnetic radiation of laboratory model of stationary plasma thruster SPT-70 developed by the Research Institute of Applied Mechanics and Electrodynamics of the Moscow Aviation Institute is described. Measurements of noise emissions were carried out on a vacuum installation with a “radiotransparent” compartment and a shielded echo-free camera in the frequency range of 1–12 GHz for typical discharge capacities (600, 800, and 1000 W), vertical and horizontal polarization, and various working substances used (krypton and xenon). The conducted studies have allowed obtaining new comparative results of the assessment of spectral characteristics of SPT-70 radiation for standard modes and prospective working bodies within the orthogonal polarization bases. The new results should include information about the radiation characteristics of SPT-70 in the time area. It is shown that the transition from xenon to krypton retains the pulsed nature of the radiation of a stationary plasma thruster, leading not only to an increase in the amplitude of pulses, but also to an increase in the frequency of repetition of “bursts” and an increase in their duration, which requires additional measures to ensure electromagnetic compatibility in order to preserve the functional safety of the spacecraft. PubDate: 2023-10-01
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Abstract: In this study, the variations of cosmic ray intensity (CRI) and their correlations with solar wind parameters and geomagnetic indices from different stations are investigated. In this work, CRI data obtained from the neutron monitor database over the MWSN, DOMC, and HRMS stations was used. The findings of this study indicate that the CRI over the MWSN station was greater than over the DOMC and HRMS stations. However, the CRI over DOMC is much lower than for MWSN and HRMS stations. Interestingly, the CRI values at all stations decreased during a strong geomagnetic storm period in May 2017 compared to January 2020. Also, the continuous wavelet transform (CWT) result showed that a higher power spectrum in CRI was clearly seen in May 2017 than in January 2020. This is because cosmic ray intensity is more highly modulated by the strength of geomagnetic storms (strong storms) than weak storms and the southward shifts of the interplanetary magnetic field (IMF Bz) component. Noticeably, CRI is found to decrease in a pattern similar to Earth’s magnetic field, and the Dst-index indicates that disturbances of the ring current cause the value of CRI to decrease upon reaching Earth. The correlation analysis of CRI over DOMC, MWSN, and HRMS stations along with the solar wind parameters and geomagnetic indices for both strong and moderate events found that the coefficients of interplanetary electric field (IEF Ey), f10.7-index, Kp, and Ap-indices peak with a very high value of 1 for a zero lag, which shows a good positive correlation between the parameters. However, the coefficients of the IMF Bz, solar wind speed, and Dst-index peak with very high values of 0.2 and 0.5 for a zero lag, indicating weaker and stronger correlations between the parameters that were taken into account for the study. PubDate: 2023-10-01
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Abstract: This article presents the results of 1000-h tests of a radiofrequency ion thruster (RFIT) with electrodes of an ion-extraction system made of carbon–carbon composite material based on the non-woven carbon frame. The quality of the surface of the thruster IES accelerating electrode being the key element of the RFIT from the lifetime point of view was assessed by visual examination and scanning electron microscopy. The maximum depth of erosion cavity on the accelerating electrode surface was determined. Electrode-surface elemental analysis was performed by the method of electron-probe microanalysis. PubDate: 2023-10-01
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Abstract: The problem of calculation of low-energy impulse trajectories to halo orbits in the vicinity of the L2 point of the Earth–Moon system is considered. A new method for calculating the trajectories of a single-impulse low-energy flight to a halo orbit is presented. The limited problem of four bodies is analyzed, within which the attraction of the Earth, Moon, and Sun is taken into account, and their position and speed are calculated using high-precision ephemeris support. Particular attention in the development of the method is paid to ensuring its computational stability for calculating trajectories with a long stay of a spacecraft (SC) in the zone of weak stability near the boundary of the Hill sphere of the Earth. The results of the calculation of single-impulse transfer trajectories from low Earth orbit to halo orbit around the L2 point of the Earth–Moon system are given. The analysis of the dependence of the main characteristics of single-impulse trajectories from the date of approach to the halo orbit is carried out. PubDate: 2023-10-01
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