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11.
We show that the retrospective evolution method yields excessively large inaccuracies in determining the age of meteorid streams. The cause is in its sensitivity to the errors in the initial conditions. The study was fulfilled with the Geminid, Quadrantid, Orionid, Perseid, and Leonid meteor showers as an example. 相似文献
12.
Andreev V. P. Zhakovshchikova T. K. Ryabova V. N. Sorokoletova E. F. Sharygin A. A. 《Water Resources》2003,30(4):427-433
The results of studying the concentration of chlorophyll in the water suspension (analysis of biomass, number, and species composition of phyto- and zooplankton) are used to estimate the trophic characteristics and saprobity of water bodies and streams of the Noril'sko-Pyasinskaya System. It has been found that during the period of the most intense operation of the Noril'sk Mining and Metallurgical Plant, the minimum values of plankton number and biomass become typical of the southern part of Pyasino Lake. The state of biota during extraordinary late spring flood and especially cold trans-polar summer has been studied. 相似文献
13.
The results of [O/Na] abundance modelling in globular clusters NGC 2808 and NGC 6752 are presented. An evolutionary scenario that is able to reproduce the characteristic observational peculiarities of the [O/Na] distribution function for the stars is proposed, which assumes that the source of the observed chemical anomalies is slow winds from massive rotating stars. The peculiarities of the chemical compositions of globular clusters can be explained in amodel with partialmixing of the stellar-wind material and the surrounding interstellar gas; i.e., second-generation stars are born in the vicinity of individual massive first-generation stars, from the heterogeneously distributed material ejected from their surfaces. 相似文献
14.
The relationship between the masses and metallicities of galaxies could be non-monotonic, due to the outflow of matter in
these systems. It is shown using a simple, one-zone, chemical-dynamicalmodel that the metallicity should be a non-monotonic
function of the mass for spheroidal dwarf galaxies with low masses of M ≤ 108
M
⊙, and a monotonically growing function for galaxies with higher masses. This is consistent with observations. 相似文献
15.
Asteroid 1620 Geographos: I. Rotation 总被引：1，自引：0，他引：1
This study is part of a wide investigation, the goal of which is to find out whether meteor streams genetically related to asteroid 1620 Geographos exist and when and how they were formed. One of the possible mechanisms of the particles' removal from the asteroid's surface is their throw-off caused by rotational forces. The asteroid-rotation parameters were defined using the sidereal rotation period and another period of 0.8 days, which was obtained from observations and identified as nutational. Small oscillations of the asteroid's rotation axis were revealed. It was also found that the rotary acceleration does not exceed the gravitational one for all possible modes of the asteroid's rotation. The gravitational-force moment caused by the Sun's attraction and the light-pressure torque have a weak influence on the rotational motion; they have not essentially changed the rotation-pole position over the past 30 orbital periods. 相似文献
16.
Mathematical modelling of the Geminid meteoroid stream 总被引：1，自引：0，他引：1
G. O. Ryabova 《Monthly notices of the Royal Astronomical Society》2007,375(4):1371-1380
17.
Deep stellar photometry of one of the most distant Galactic globular clusters, Palomar 3, based on frames taken with the VLT in Johnson–Cousins broadband V and I filters is presented, together with medium-resolution stellar spectroscopy in the central region of the cluster obtained with the CARELEC spectrograph of the Observatoire de Haute Provence and measurements of the Lick spectral indices for the integrated spectrum. Computations of the orbital parameters of Palomar 3 and nine Galactic globular clusters with similar metallicities and ages are also presented. The orbital parameters, age, metallicity, and distance of Palomar 3 are estimated. The interstellar absorption is consistent with and supplements values fromthe literature. The need to obtainmore accurate data on the propermotions, ages, and chemical compositions of the cluster stars to elucidate the origin of this globular cluster is emphasized. 相似文献
18.
This paper presents the results of experimental investigations of variations in maximal usable frequencies (MUFs) during solar eclipses with the use of the method of panoramic tilt sounding by chirps in Eastern Europe and Western Siberia. The characteristics of perturbations of MUFs have been obtained experimentally. It has been established that the effective recombination coefficient increases by 24% in the ionospheric F region with an increase in the maximum eclipse phase from 0.49 to 1.0. 相似文献
19.
20.
Collisionless plasma of the solar wind is considered. A number of physical processes in this plasma lead to the formation of magnetic islands that are potential traps for charged particles. The merging and contractions of magnetic islands cause a powerful acceleration of these particles to energies over 1 MeV. This work continues the study in recent years on modeling of the acceleration of charged particles of the solar wind. Our analytical solution of the transport equations allowed us to find the exact number of particles with energies exceeding given level. 相似文献