Kinematics and Physics of Celestial Bodies最新文献

A quantitative analysis of the spectrum of HD 108564 is performed. It is a star of the main sequence of spectral class K5V, the atmosphere of which is depleted in metals. The high-quality observed HARPS spectra are downloaded from the ESO archive. Abundances of elements in the atmosphere are obtained by fit of observational profiles of the C I lines and selected lines of the C₂ molecules, and the O I, Ca I, Si I, Sc II, Cr I, CI, OI, Na I, Mg I, Si I, Ca I, Sc II, Ti I, Ti II, Cr I, Mn I, Fe I, Fe II, Co I, Ni I, Cu I, and Zn I. Abundances are determined iteratively, with a recalculation of the input parameters, which are effective temperature T_eff  at a fixed value of gravity logg (or log g for a fixed T_eff value). The effect of variations of T_eff  or log g, which provide the same abundances of A(Fe I) and A(Fe II), on the abundances of other elements are determined. The obtained results indicate an excess of light elements (C, O, and Si) compared to the group of iron. The absence of the lithium line at 670.8 nm is confirmed with an estimate of A(Li) < –12.5 for the upper limit of lithium abundance in the abundance scale, in which the sum of all abundances is 1.0. The determined radial velocity equal to V_rad = 111.21 km/s is consistent with the known estimates of other researchers. Apparent rotation velocity V sin i = 1.12 ± 0.5 km/s is determined.

We investigated the possibility of generating kinetic Alfvén waves by beams of high-speed protons in front of the Earth’s main shock wave. An analytical solution is obtained for the hose-type instability of kinetic Alfvén waves caused by the beam’s dynamic pressure. The effect of the temperature of high-speed beams and the temperature of solar wind protons on the characteristics of the generated disturbances is studied. The temperature has a significant effect on the transverse scales of disturbances: the higher the temperature of the beam protons and the lower the temperature of the surrounding plasma, the more stringent the restrictions imposed on the transverse wavelength scales. The development of instability during the propagation of beams of reflected, intermediate, and diffused protons in the region ahead of the Earth’s main shock wave is considered. The dynamics of the movement of disturbances in this region are analyzed.

In this paper, we have improved the Hyades members with aid of the Gaia EDR3 source. We have studied their kinematics, including computations of the convergent point with AD-diagram method such as (left( {{{A}_{0}},~{{D}_{0}}} right) = left( {79^circ .48 pm 0^circ .11,~,,6^circ .85 pm 0^circ .38} right)), their spatial velocities (U,~V,~W,{text{(km}};{{{text{s}}}^{{ - 1}}}{text{)}}), their morphology with 3D. A relation was established for Hyades stars between their Galactic coordinates (left( {l,~b} right)) and the angular distances (left( {{lambda }} right)) from the vertex. The precision criteria of this relation are very satisfactory and a correlation coefficient of value ( approx 0.90) was found which proves that the attributes are completely related linearly.

Solar storms accompanied by solar flares, coronal mass ejections, and high-speed flows result in considerable disturbances in the Sun–interplanetary medium–magnetosphere–ionosphere–atmosphere–Earth (internal geospheres) system. As a result, geospace storms with synergistically interacting magnetic, ionospheric, atmospheric, and electrical storms arise in our planet. Magnetic and ionospheric storms have been studied for a long time, but atmospheric storms and electrical storms have been studied considerably to a less extent. Geospace storms and their components exhibit significant variability. It may be asserted that no identical two storms exist. Therefore, a comprehensive study of each new geospace storm and its manifestations and features is an urgent scientific issue. This will contribute to a process of their adequate simulation and, in the long term, forecasting. The purpose of this article is to describe the observed features of the ionospheric and magnetic storms accompanying the geospace storm on December 21–24, 2016. The state of the geomagnetic field has been observed via the fluxgate magnetometer located at the Magnetometer Observatory of the Karazin Kharkiv National University (49°38′ N, 36°56′ E). The dynamics of the ionospheric plasma has been monitored by a vertical incidence Doppler radar and a digisonde located at the Radio Physics Observatory of the Karazin Kharkiv National University (49°38′ N, 36°20′ E). The Doppler radar operate at 3.2 and 4.2 MHz; however, only measurements performed at 3.2 MHz are given below, since a frequency of 4.2 MHz turned out to be inefficient at nighttime when F2 layer critical frequency median f_{0 F2} ≈ 2 MHz, which prevented signal reflection from the ionosphere even at 3.2 MHz. Prior to the beginning of the magnetic storm on December 20, 2016, the level of the H and D components rarely exceeded 0.2–0.7 nT. The sudden commencement of a storm between 06:00 and 10:00 UTC virtually did not affect this level. During the second half of the day on December 21, 2016, the level of exhibited sporadic fluctuations increased from approximately 1 to 3–4 nT. During the next few days, up to December 25, 2016, their level showed variations mostly from approximately 1 nT to approximately 2 nT. Increases in the level were predominantly observed in the period from 05:00 to 15:00 UTC for the H component and from 10:00 to 20:00 UTC for the D component. The weak (power 20 GJ/s and energy approximately 0.45 PJ) geospace storm in the period of December 21–24, 2016, was accompanied by a moderate positive ionospheric storm, as well as by three negative ionospheric storms, one of which was very strong, and the other two were strong and moderate. The geospace storm was accompanied by a moderate magnetic storm with an energy of approximately 2 PJ and a power of approximately 56 GW. The positive ionospheric storm barely affects the level of the signal reflected from the ionospher

We here analyzed the effects of viscosity, oblateness of the primary m₁, length parameter l, and perturbations in the Coriolis and centrifugal forces on the stability of the equilibrium points of the Robe’s problem. In the setting, it is assumed that the two primaries m₁, an oblate spheroid of incompressible homogeneous viscous fluid of density ρ₁ and m₂, a finite straight segment of length 2l revolve around their common center of mass in circular orbits while third body m₃ (a small solid sphere of density ρ₃) moves inside m₁. Two collinear {L₁, L₂} and infinite non-collinear equilibrium points are evaluated and found that the location of equilibrium points remain unaffected by viscosity. However, the effects of oblateness and perturbation in the centrifugal force are quite noticeable from the expressions of the equilibrium points. The stability criterion for L₁ and L₂ are stated whereas the non-collinear equilibrium points are found to be unstable. It is observed that the viscosity has a substantial effect on the stability as it changes the nature of stability from marginal stability to asymptotic stability. The perturbations do not affect the stability of L₁ but affect the stability of L₂. Moreover, the effect of oblateness on the stability of the equilibrium points is quite evident. A very important observation of the study is that the oblateness parameter A neutralizes the effects of the length parameter l and perturbation ε₂, on the stability of equilibrium point L₁. The results obtained are applied on Earth-Moon, Jupiler-Amalthea, Jupiler-Ganymede systems (astrophysical problems) to predict the stability of L₁.

A historical research study devoted to the elucidation of the historical facts about the activity of the Kharkiv Astronomical Observatory during the German–Soviet War is carried out. The astronomical community of Kharkiv suffered heavy losses: Professors O.I. Razdol’skii, M.S. Savron, and S.M. Semiletov, Researcher G.L. Strashnii, Yu.M. Fadeev, and V.O. Balanskii, and calculation specialist L.M. Kostirya died; young representatives of the Kharkiv astronomical community M. Azbel’, F. Berezovskii, I. Tymoshenko, and O. Ubiivovk gave their lives in the battle with the enemy. During warfare, many observatory buildings, together with astronomical instruments and devices, were seriously damaged. The peculiarities of observatory operation during the studied period have been documented, and the biographical data of most of the employees of the Kharkiv Astronomical Observatory during the Nazi occupation of the city in 1941–1943 have been clarified. The stages of restoration of the observatory after the liberation of Kharkiv from the invaders were considered.