Abstract: This paper provides a brief description individual elements that can be included in the Solntse–Terahertz scientific apparatus that was designed for the first time to carry out an extra-atmospheric experiment onboard the International Space Station. Its purpose is to measure terahertz electromagnetic radiation both from the quiet Sun and during active processes on the Sun (solar flares, coronal mass ejections, etc.), which is necessary to establish the physical nature of solar activity and solar flares. The possibility is discussed of using optoacoustic converters (Golay cells) as receivers of terahertz radiation, the sensitivity, stability, and response time of which were determined in the course of preliminary laboratory studies under terrestrial conditions. PubDate: 2021-01-01
Abstract: A numerical solution of the wave equations for whistler electromagnetic waves incident on the ionosphere from above is obtained. For the calculations, we used a matrix algorithm for the approximate solution of wave equations in a stratified smoothly inhomogeneous medium and the collocation method for solving the boundary problem. Dependences of reflection coefficients R are obtained and analyzed on the frequency and angle of incidence of the wave for different seasons and time of day. At night, for waves with frequencies from 1 to 10 kHz, the values of R vary from 0.1 to 0.7. In daytime conditions, the value of R, on average, is two orders of magnitude lower and does not exceed 0.04. The smallest values of the reflection coefficient are associated with waves, the reflection of which occurs in the region of strong attenuation at heights of 80–110 km. The results obtained explain the specific features of the conditions for the excitation of the plasma magnetospheric maser. PubDate: 2021-01-01
Abstract: — Energetic electron precipitation (EEP) into the atmosphere is one of the mechanisms of depleting the Earth’s outer radiation belt. Precipitating electrons generate bremsstrahlung that penetrates the stratosphere and is recorded by detectors on balloons. However, these observations can be carried out only when the balloon is located at altitudes higher than ~20 km. The near-Earth POES satellites are constantly recording the fluxes of precipitating electrons in the loss cone, but they move too quickly in the space. In this paper, EEPs are compared on the basis of observations in the stratosphere and on satellites during 2003 and estimates of a number of EEP events at Apatity are obtained, assuming that the radiosonde was continuously located at an altitude higher than 26 km. PubDate: 2021-01-01
Abstract: In the process of deploying the wings of solar arrays of a spacecraft, natural transverse vibrations arise in them. The study of these vibrations is an urgent problem, since in some cases they are capable of disrupting the commutation of photoelectric converters. The transverse vibrations of the wing originate from the connection of its sections when locking (coupling) hinge devices. In this case, the kinetic energy of the sections is converted into the potential energy of natural vibrations of the solar array wing. This problem is traditionally solved by using a finite element model with subsequent calculations in the ANSYS program. The purpose of this study is to develop an approximate analytical method for mathematical modeling of the natural elastic vibrations of elements of the solar array wing arising in the process of its deploying. PubDate: 2021-01-01
Abstract: — This paper presents an analysis of wave activity recorded by the MMS satellites during a prolonged dipolarization in the near magnetotail (XGSM ~ –17 RE). It was found that multiple narrow-band, quasi-parallel whistler wave bursts were observed behind the leading front of dipolarization, during the phase of growth of the magnetic field’s BZ component. The durations of wave bursts were ~1–15 s, and the characteristic frequencies ranged from ~0.1 to 0.8 fc (fc is the electron gyrofrequency). Based on a detailed analysis of a single wave burst, it was found that the frequency corresponding to the maximum value of a linear increment of quasi-parallel whistler waves was close in magnitude to the observed frequency, which indicates the possibility of satellite location close to the source of waves. We also demonstrated that, in the case under discussion, the electrons with pitch angles of 125°–135° and energies of ~3–12 keV made a largest contribution to the increment of whistler waves. These observations have shown that, during dipolarizations, the thermal and suprathermal electron populations are most effectively involved in resonant interaction with whistler waves. PubDate: 2021-01-01
Abstract: A direct method for optimizing the spatial trajectories of lunar landing in the deceleration phase with a limitation along the descent profile, when the lander must remain inside a certain cone with apex at a given landing point, is presented. The model of motion is a point of variable mass moving in a uniform gravitational field. The method uses a two-level optimization of the characteristic velocity for a given distance and lateral displacement at free landing time. The upper level corresponds to one-dimensional nonlinear optimization of the landing time. The lower level corresponds to optimization for the landing times established at the upper level and the given coordinates of the landing point using discrete sets of pseudopulses and high-dimensional linear programming. Energetically accessible regions and regions when redetermining the landing point are presented as examples. PubDate: 2021-01-01
Abstract: A review of publications on the problems of monitoring of clogging near-Earth space by natural space debris, including hazardous meteoroids, using methods of optical meteor astronomy is carried out. Both observation methods and methods for estimating the danger from natural space debris for spacecraft are analyzed. PubDate: 2021-01-01
Abstract: A new concept of a space experiment with a γ-ray spectrometer onboard a mobile spacecraft has been proposed for studying the elemental composition of the Moon, Mars, and other celestial bodies without an atmosphere or with a thin atmosphere using the method of tagged charged particles of galactic cosmic rays. This technique makes it possible to eliminate almost fully the background of γ-radiation from the spacecraft with the instrument installed onboard and significantly increase the spatial resolution for studying the elemental composition of matter along the mobile spacecraft trajectory. PubDate: 2021-01-01
Abstract: Increasing frequencies of perspective space mirror antennas functioning leads to a significant tightening of the requirements for the accuracy and stability of the reflecting surface of the used reflectors. However, the provision of high requirements is technically difficult to implement. Hence, the problem of Pareto-optimal design of parabolic antenna reflectors with a relatively high signal amplification coefficient and minimum requirements for the accuracy of the reflecting surface profile is formulated. We obtained analytical estimates for Pareto fronts of various ranks characterizing the accuracy of the profile of the reflecting surface of the antenna parabolic reflector depending on its diameter and the range of operating frequencies required to ensure a high signal gain. PubDate: 2021-01-01
Abstract: The paper presents machine-learning models for predicting powerful solar flares and background X-ray fluxes in the range of 1–8 Å. To predict solar flares for the next day, information was used on the current level of solar activity obtained from ground-based synoptic observations, such as characteristics of sunspots and radio fluxes at wavelengths of 10.7 and 5 cm, as well as the level of the background flux and the number of solar flares of the current day obtained from the GOES satellite. To predict the background fluxes of X-ray radiation, only data from ground-based telescopes were used. The high efficiency of the forecast for the next day is shown. The neural network was trained on data available since 2002. PubDate: 2020-11-01 DOI: 10.1134/S0010952520060106
Abstract: When spacecraft cross the heliospheric plasma sheet (HPS) that separates large-scale magnetic sectors of opposite directions in the solar wind, multiple rapid fluctuations in the sign of the magnetic radial component are often observed. These fluctuations indicate the change of the sign of the azimuth electric current density within the HPS. Possible mechanisms of formation of the multilayered current structure of the HPS are proposed. Within the context of a stationary magnetohydrodynamic solar wind model, we test one of the most popular hypotheses regarding an extension of multiple current sheets from the streamer belt oriented along the neutral line of the solar magnetic field into the solar wind. Properties of self-consistent distributions of the solar wind key characteristics are investigated as function of the fine structure of streamers. The results show that both single and multiple streamers can be the source of the set of a multilayered structure with alternating azimuthal currents. The significance of the results for the interpretation of solar wind data is discussed. PubDate: 2020-11-01 DOI: 10.1134/S0010952520060076
Abstract: A self-consistent hybrid model of a thin current sheet (TCS) with a thickness of the order of several ion gyroradii is proposed that takes into account the multicomponent nature of collisionless space plasma. Several plasma components can be present in the tails of the magnetospheres of terrestrial planets (for example, the Earth, Mercury, Mars, and Venus). Variations in the current sheet (CS) structure in magnetospheric plasma in the presence of heavy oxygen ions with different characteristics are analyzed. It is shown that high relative concentrations of oxygen ions, as well as their relatively high temperatures and drift velocities, lead to significant thickening of CS and the formation of an additional embedded scale. In this case, on the profiles of the main characteristics—current density and magnetic field—symmetric breaks appear, which correspond to a sharp change in the gradients of variation in values. A comparison is performed and a qualitative agreement is shown between the simulation results and observational data in the tail of the Martian magnetosphere. PubDate: 2020-11-01 DOI: 10.1134/S0010952520060039
Abstract: This work is devoted to the study of properties of spectra of turbulent solar wind fluctuations in plasma compression regions, such as CIR (the plasma compression regions in front of high-speed streams from coronal holes) and SHEATH (the compression regions in front of interplanetary manifestations of coronal mass ejections EJECTA and magnetic clouds MC). The spectra of ion flux fluctuations, on both magnetohydrodynamic and ion-kinetic scales, are considered on the basis of data from the BMSW spectrometer on the SPEKTR-R spacecraft with a high (up to 31 ms) time resolution. The comparison of turbulent characteristics in the plasma compression regions and in the undisturbed solar wind is carried out both on a separate example and using extensive statistical material. It is shown in the paper that the turbulent cascade characteristics on the kinetic interval can significantly change in the plasma compression regions, and the signatures of a change in the main processes that determine the energy dissipation are revealed in them, which may cause increased heating in the regions under consideration. PubDate: 2020-11-01 DOI: 10.1134/S001095252006009X
Abstract: The magnetosheath is an integral element of solar–terrestrial relations. The paper analyzes the influence of the solar wind parameters and their variability, as well as the topology of the bow shock on the characteristics of plasma turbulence in the magnetosheath on scales corresponding to the transition from the inertial region of a turbulent cascade to the dissipative one. The analysis is based on extensive statistics of measurements of the BMSW instrument with high time resolution on board the Spektr-R satellite in the magnetosheath in 2011–2018. It is shown that the variability of the solar wind plasma density and the interplanetary magnetic field magnitude, as well as the angle between the normal to the bow shock and the interplanetary magnetic field has the greatest influence on the form of the turbulent cascade directly behind the bow shock. PubDate: 2020-11-01 DOI: 10.1134/S0010952520060088
Abstract: An experiment on radio sounding of the circumsolar plasma by signals from the Mars Express spacecraft in 2013 was carried out in the period from March 4 through May 31. The investigated characteristics were the frequency of signals in the centimeter and decimeter ranges and the differential frequency. A number of events were recorded in which the intensity of the frequency fluctuations of the signals probing the plasma was several times higher than the background values. As shown by the analysis of observations of solar activity, such as an increase in the flux of X-rays and SOHO LASCO coronagraph data, this is explained by the passage of disturbed plasma streams generated in the solar corona through the spacecraft radio communication path with the Earth. The comparison of the radio transmission data with the results of measurements of the parameters of the near-Earth plasma using the Wind spacecraft in adjacent periods of time. As a result of the analysis of the data on the proton concentration, it became clear that sharp increases in both the average values and fluctuations of this characteristic were also observed near the Earth. The time lag between the events observed in the circumsolar and near-Earth plasma shows that the cause of the disturbances is the increased activity of the same coronal region rotating with the Sun. PubDate: 2020-11-01 DOI: 10.1134/S0010952520060040
Abstract: One perturbed type of solar wind and magnetospheric disturbance drivers is the compression region in front of fast ICMEs—the Sheath region. In front of this region, an interplanetary shock is observed in approximately half of cases. However, the parameters and their time profiles in these two types of the Sheath region differ comparatively little. Therefore, the Sheath region without a shock is as geoeffective as the Sheath region with a shock: the Sheath region in the first case generated almost 10% of magnetic storms with a minimum Dst < –50 nT of all the magnetic storms for 1976–2017 with identified interplanetary drivers. Many authors do not analyze this driver (for this reason, we call it the “lost driver”); therefore, their studies contain incorrect conclusions on solar–terrestrial physics. PubDate: 2020-11-01 DOI: 10.1134/S0010952520060052
Abstract: — The structure of interplanetary shock fronts was studied based on the data from the BMSW plasma spectrometer, installed on the SPEKTR-R spacecraft, supplemented by magnetic field measurements on the WIND spacecraft. Special attention was paid to periodic growths (overshoots) in the value of the ion flux or magnetic field relative to their mean values outside the ramp. A comparison was performed with the overshoot in the magnetic field, with the Mach number, and with the β parameter. Based on an analysis of 18 intersections of interplanetary shock fronts, in which the overshoots in the ion flux and magnetic field value were observed, it was shown that the value of the magnetic field overshoot is, on the average, less than a similar value in the solar wind’s ion flux, which is associated with different time resolution of measurements. The ion flux overshoot value is found to grow with the growth of the Mach number, in the same way, as the value of the magnetic field overshoot. It is shown that overshoots are formed not only in the supercritical shocks, but also in those with Mach numbers that are less than the value of the first critical Mach number. It is also found that the estimates of the wavelength of the ion flux and magnetic field oscillations behind the ramp well correlate with the value of a gyroradius of captured ions. PubDate: 2020-11-01 DOI: 10.1134/S0010952520060015
Abstract: A critical review of the hypothesis of the Big Bang and accompanying expansion of the Universe is presented. A conclusion is drawn that proof of it is absent. Explanations of the redshift of galaxies and the relic background without involving relativistic ideas are proposed. PubDate: 2020-11-01 DOI: 10.1134/S001095252005010X
Abstract: The characteristics and course of development of the current 24th solar activity (SA) cycle allow it to be considered a cycles in an epoch of lowered SA. Comparison of evolutionary changes in the cycles of different epochs in the phases of the minimum made it possible to distinguish two groups by the rate of decline. The first group with a relatively fast decline (~15 months) includes all cycles of epochs of increased SA, transition periods, and cycle 16 from the epoch of lowered SA. The second, with a slow decline (~40 months), contains the rest of the cycles of epochs of lowered SA, including the current 24th one, the minimum of which can be expected in the first half of 2020. PubDate: 2020-11-01 DOI: 10.1134/S0010952520060064
Abstract: We investigate a procedure for determining the shadow cone of the Earth in the course of the motion of a satellite in the ecliptic plane. The average time spent by the satellite in the Area of the Earth’s shadow is estimated depending on the orbit parameters in the outer sphere of the Earth’s gravitational influence. The obtained estimate of the average time spent by the satellite in the shadow allows us not to take the shadow into account in the qualitative analysis of satellite motion. The results obtained for a conical shape of the shadow are compared with the results obtained for a cylindrical shape, and a choice is made in favor of the conical one. PubDate: 2020-11-01 DOI: 10.1134/S0010952520060027
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