Different magneto-rotational supernovae     

G. S. Bisnovatyi-Kogan  S. G. Moiseenko  N. V. Ardelyan 《Astronomy Reports》2008,52(12):997-1008

We present the results of two-dimensional calculations of a magneto-rotational (MR) supernova explosion with a collapsing core for various core masses, rotational angular momenta, and magnetic-field configurations. It is shown that the MR mechanism produces an explosion energy that corresponds to observed values. The form of the explosion depends substantially on the initial configuration of the magnetic field. MR instability develops during the evolution of the magnetic field in an MR supernova explosion, resulting in an exponential increase of all components of the magnetic field, thereby substantially decreasing the time scale of the MR explosion. The energy of the supernova increases with the core’s mass and initial rotational energy.  相似文献   

Collapse of the spherical stellar system     

L. R. Yangurazova  G. S. Bisnovatyi-Kogan 《Astrophysics and Space Science》1984,100(1-2):319-328

A new numerical method is proposed for solving the problems connected with the evolution of spherical clusters. The method is based upon the solution of the algebraic equations describing the motions of spherical shells.The stage of the collapse of a typical cluster is considered. The initial configuration is taken as a system with a uniform density distribution and with velocities much less than the virial ones. The model close to a stationary one has been obtained. The mass of the stationary cluster comprises about 60% of the initial one. The density distribution of the outer part of the cluster approximately corresponds to a profile of R ^–3.3.  相似文献   

Assimilating data into open ocean tidal models     

Gennady A. Kivman 《Surveys in Geophysics》1997,18(6):621-643

The problem of deriving tidal fields from observations by reason of incompleteness and imperfectness of every data set practically available has an infinitely large number of allowable solutions fitting the data within measurement errors and hence can be treated as ill-posed. Therefore, interpolating the data always relies on some a priori assumptions concerning the tides, which provide a rule of sampling or, in other words, a regularization of the ill-posed problem. Data assimilation procedures used in large scale tide modeling are viewed in a common mathematical framework as such regularizations. It is shown that they all (basis functions expansion, parameter estimation, nudging, objective analysis, general inversion, and extended general inversion), including those (objective analysis and general inversion) originally formulated in stochastic terms, may be considered as utilizations of one of the three general methods suggested by the theory of ill-posed problems. The problem of grid refinement critical for inverse methods and nudging is discussed.  相似文献   

The North of Eastern Siberia: Refuge of Mammoth Fauna in the Holocene     

Gennady G. Boeskorov   《Gondwana Research》2004,7(2):451-455

The global climate changings at the end of Pleistocene led to extinction of the typical representatives of Mammoth fauna–mammoth, woolly rhinoceros, wild horse, bison, muskox, cave lion, etc.–on the huge territories of Northern Eurasia. Undoubtedly the Mammoth fauna underwent pressure from the Upper Paleolithic Man, whose hunting activity also could play the role in decreasing the number of mammoths and other representatives of megafauna (large mammals). Archaeological data testify that the typical representatives of Mammoth fauna were the Man's hunting objects only till the end of the Pleistocene. Their bone remains are not usually found on the settlements of Mesolithic Man. Formerly it was supposed that the megafauna of ‘Mammoth complex’ was extinct by the beginning of Holocene. Nevertheless the latest data testify that the global extinction of the Mammoth fauna was sufficiently delayed in the north of Eastern Siberia. In the 1990s some radiocarbon data testified that the mammoths on the Wrangel Island existed for a long time during the Holocene from 8000 till 3700 y. BP. The present radiocarbon data show that wild horses inhabited the north of Eastern Siberia (the lower stream of the Enissey river, the Novosibirskie Islands, the East Siberian sea-shore) 3000–2000 y. BP. Musk-oxen lived on the Taimyr Peninsula and the Lena River delta about 3000 y. BP. Some bison remains from Eastern Siberia belong to the Holocene. The following circumstances could promote the process of preservation of the Mammoth fauna representatives. The cool and dry climate of this region promotes the maintenance of steppe associations – habitats of those mammals. The Late Paleolithic and Mesolithic settlements are not found in the Arctic zone of Eastern Siberia from the Taimyr Peninsula to a lower stream of the Yana River; they are very rare in the basins of the Indigirka and Kolyma Rivers. So, the small number of the Stone Age hunting tribes on the North of Eastern Siberia was another factor in the long-term preservation of some Mammoth fauna representatives.  相似文献   

The afterglow of a dense molecular cloud after the passage of a cosmological gamma-ray burst     

M. V. Barkov  G. S. Bisnovatyi-Kogan 《Astronomy Reports》2005,49(8):611-623

Bolometric light curves for the afterglow resulting from the passage of a gamma-ray burst through a molecular cloud are computed. The profile and duration of the afterglow light curve depend strongly on the distribution of matter in the cloud, the degree of collimation of the gamma-ray radiation, and the observing conditions. The peak can be reached as soon as seven days (the gamma-ray burst is located at some distance from the center of a molecular cloud with small-scale density enhancements), or as long as one to three years (the gamma-ray burst is located at the center of a uniform molecular cloud) after the burst. The bolometric luminosity of the re-radiated signal can reach 6.5 × 10⁴² erg/s.  相似文献   

The first record of “spelaeoid” bears in Arctic Siberia     

Andrei V. Sher  Jacobo Weinstock  Gennady F. Baryshnikov  Sergey P. Davydov  Gennady G. Boeskorov  Vladimir S. Zazhigin  Pavel A. Nikolskiy 《Quaternary Science Reviews》2011,30(17-18):2238-2249

For a long time, “spelaeoid” (cave-bear-like) bears, Ursus (Spelearctos) spp., were believed to be almost purely European animals. Their geographic range has recently been extended to the east, in southern Siberia, Transbaikalia, Kirghizia, Mongolia and Korea. Two unexpected new findings, presented here in detail, significantly change existing views on the distribution of cave bears; both were found in North-Eastern Siberia, far beyond the Arctic Circle, more than 1500 km to the north-east of the previously accepted range.One of the fossils is a mandible, found near the town of Cherskiy at 68.73°N, 161.38°E. The analysis of local geology and accompanying mammal fossils suggests that it comes from the Olyorian Fauna (Early to early Middle Pleistocene). Morphologically, the Cherskiy mandible is closest to Ursus savini, a small middle Pleistocene cave bear from the British Cromer Forest-bed Formation, but differs in having a slightly more advanced dentition, and thus it is described as a new subspecies Ursus savini nordostensis. Another newly recognized fossil of the “spelaeoid” bear is an astragalus found at the Oskhordokh site at 67.54°N, 135.67°E, on a large gravel bar on the right bank of the Adycha River. This specimen is attributed to Ursus cf. deningeri.The paper also presents an interesting example of the interaction between classical and “molecular” palaeontology.The new finds significantly change existing ideas on the ecology and evolution of cave bears, some of the most remarkable members of the extinct Pleistocene megafauna.  相似文献   

An Anisotropic Cosmic-Ray Enhancement Event on 07-June-2015: A Possible Origin     

Agnieszka Gil  Gennady A. Kovaltsov  Vladimir V. Mikhailov  Alexander Mishev  Stepan Poluianov  Ilya G. Usoskin 《Solar physics》2018,293(11):154

A usual event, called anisotropic cosmic-ray enhancement (ACRE), was observed as a small increase (\({\leq}\,5\%\)) in the count rates of polar neutron monitors during 12?–?19 UT on 07 June 2015. The enhancement was highly anisotropic, as detected only by neutron monitors with asymptotic directions in the southwest quadrant in geocentric solar ecliptic (GSE) coordinates. The estimated rigidity of the corresponding particles is \({\leq}\,1\) GV. No associated detectable increase was found in the space-borne data from the Geostationary Operational Environmental Satellite (GOES), the Energetic and Relativistic Nuclei and Electron (ERNE) on board the Solar and Heliospheric Observatory (SOHO), or the Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA) instruments, whose sensitivity was not sufficient to detect the event. No solar energetic particles were present during that time interval. The heliospheric conditions were slightly disturbed, so that the interplanetary magnetic field strength gradually increased during the event, followed by an increase of the solar wind speed after the event. It is proposed that the event was related to a crossing of the boundary layer between two regions with different heliospheric parameters, with a strong gradient of low-rigidity (\({<}\,1\) GV) particles. It was apparently similar to another cosmic-ray enhancement (e.g., on 22 June 2015) that is thought to have been caused by the local anisotropy of Forbush decreases, with the difference that in our case, the interplanetary disturbance was not observed at Earth, but passed by southward for this event.  相似文献   

Numerical Simulations of Magnetized Astrophysical Jets and Comparison with Laboratory Laser Experiments     

V. S. Belyaev  G. S. Bisnovatyi-Kogan  A. I. Gromov  B. V. Zagreev  A. V. Lobanov  A. P. Matafonov  S. G. Moiseenko  O. D. Toropina 《Astronomy Reports》2018,62(3):162-182

The results of MHD numerical simulations of the formation and development of magnetized jets are presented. Similarity criteria for comparisons of the results of laboratory laser experiments and numerical simulations of astrophysical jets are discussed. The results of laboratory simulations of jets generated in experiments at the Neodim laser installation are presented.  相似文献   

The construction of self-consistent models for outflowing stellar envelopes     

G. S. Bisnovatyi-Kogan  A. V. Dorodnitsyn 《Astronomy Reports》2001,45(12):995-1001

The article presents self-consistent computations of the spherically symmetric envelope of a massive (M=20M _⊙) star whose envelope is flowing outward under the action of continuum radiation pressure. A system of equations describing the out flow for arbitrary optical depth, degree of ionization, and opacity κ are obtained. A numerical solution is obtained for the case of constant κ and degree of ionization via approaching integrations from the singularities and smooth joining in the intermediate region. Asymptotic solutions are found in the vicinity of the sonic point and the singularity at infinity.  相似文献   

Modelling of global ocean tides with allowance for island effects     

Prof. Dr. Boris A. Kagan  Dr. Gennady A. Kivman 《Ocean Dynamics》1993,45(1):1-13

Summary Parameterization schemes for single islands, island chains and archipelagos are described. It is shown that their utilization within the framework of a global tidal model leads not only to local peculiarities in the spatial structure of tidal characteristics, but also to cardinal restructuring of the tidal pattern far beyond the islands and an appreciable increase (about 0.5·10¹²W) of the global tidal energy dissipation. The latter is commensurable by the order of magnitude with the imbalance between estimates of tidal energy dissipation in the World Ocean as a whole and on the continental shelf.

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Modellierung der Gezeiten der weltmeere unter Berücksichtigung von Inseleffekten

Zusammenfassung Es werden parametrisierte Darstellungen von einzelnen Inseln, Inselketten und Inselgruppen beschrieben. Es wird gezeigt, daß ihre Anwendung bei einem globalen Gezeitenmodell nicht nur zu lokalen Besonderheiten in der geographischen Struktur der Gezeiten führt, sondern auch zur grundsätzlichen Restrukturierung des Gezeitenmusters weit über die Inseln hinaus und zu einer deutlichen Zunahme (etwa 0,5·10¹² W) des globalen Gezeiten-Energieverlusts für die M₂-Tide. Dieser hat etwa die Größenordnung des Unterschiedes zwischen dem Gezeiten-Energieverlust des gesamten Weltmeeres und dem auf dem Kontinentalschelf.

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