The age and tectonic setting of volcanic and cherty sequences in the ophiolite complex of the Atbashe Ridge (Southern Tien Shan)   总被引：1，自引：0，他引：1  

D. V. Alekseev  V. A. Aristov  K. E. Degtyarev 《Doklady Earth Sciences》2007,413(2):380-383

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Structure of the inner region of the accretion disk of the Herbig Ae star CQ Tau based on long-term monitoring data     

O. V. Kozlova  D. N. Shakhovskoi  A. N. Rostopchina  I. Yu. Alekseev 《Astrophysics》2007,50(1):26-39

Results from simultaneous spectral and photometric monitoring of the Herbig Ae star CQ Tau in the neighborhood of the Hα and resonance sodium doublet Na I D lines are presented. It is shown that the inner structure of the accretion disk of CQ Tau is nonuniform and consists of two regions with quite different kinematic characteristics. Region I is characterized by relative stability and a smooth long-term variation in the velocity of the gas along the line of sight. Region II is distinguished by the highest velocities and a variability in their maximum values over time scales from a few days to 700 days. The dust clouds which produse the star’s brightness minima may also be the source of cold gas and contribute to the observed spectral variability. We assume that region I of the disk coincides with the accretion disk of the star. The kinematic differences in region II may be caused by dissipation of circumstellar dust clouds which, moving in elongated orbits, are able to approach the star quite closely. __________ Translated from Astrofizika, Vol. 50, No. 1, pp. 39–55 (February 2007).  相似文献   

Structure of the inner regions of the circumstellar gas envelopes around young hot stars. II. The new cycle of spectral activity of the Herbig Ae star HD 31648     

O. V. Kozlova  I. Yu. Alekseev  D. N. Shakhovskoi 《Astrophysics》2007,50(4):467-487

The results of the high-resolution long-term spectral monitoring of the Herbig Ae star HD 31648 in the regions of emission Hα line, Na I D resonance lines and OI 7774 lines are presented. We confirmed the conclusion, made in previous papers, that the spectral variability of the star in the region of Hα line have a cyclic character. It is manifested itself as the changing of the equivalent width and intensity of Hα line of the time scale of about 1200d. It is shown, that the stellar wind is non-homogeneous and consists of several components, which are differed each other by their velocities. They are observed as in the H line as in Na I D resonance lines. The component’s parameters are changed during the cycle of stellar activity (in the maximum of activity the velocity and density of the wind are taken the largest values and then they are gradually decreased). The investigation of rapid variability of the He I 5876 line on the time scale of a few hours allows find the correlation between the variability of the blue and the red wings of the line. It points at the connection between the accretion and the outflows. Such connection, in particularly, is predicted by the modeling of the wind from young stars made in the frame of the magneto-centrifugal model, the accordance of which for the HD 31648 was shown in the previous papers. In the present work we confirmed this conclusion on the basis of the new data. We found the weak variability of the stellar brightness (about 0.2m), which is agree with the spectral variability (the brightness of the star becomes lower in the maximum of the activity). These changes are well explained by the process of the dust transfer from CS disk by the stellar wind. This process is likely to be more effective in the maximum of activity. An analysis of the variability of other spectral lines shows the agreement between the changing of the Hα line, the Na I D resonance doublet lines and KI 7698 line. The weak connection between the He I 5876 and the Na I D lines is also found. Since the formation regions of He I 5876 and Na I D lines are essentially different, we can conclude that the phenomena, responsible for the observed cyclic variability, take place in a spacious region of the CS envelope. We believe that the most plausible reason of found cyclic variability is the reconstruction of the inner structure of the CS gas envelope, caused by the presence around the star a low mass companion or planet. __________ Translated from Astrofizika, Vol. 50, No. 4, pp. 565–588 (November 2007).  相似文献   

Geochemistry of Cenomanian/Turonian boundary sediments in the mountainous part of Crimea and the northwestern Caucasus     

M. A. Levitan  A. S. Alekseev  N. V. Badulina  Yu. P. Girin  L. F. Kopaevich  I. V. Kubrakova  O. A. Tyutyunnik  M. Yu. Chudetsky 《Geochemistry International》2010,48(6):534-554

Detailed data obtained on the chemistry of sedimentary rocks from the mountainous part of Crimea and the northwestern Caucasus that were dated at the Cenomanian/Turonian boundary and were formed during Oceanic Anoxic Event 2 (OAE 2) make it possible to calculate the dissolved oxygen concentration in the bottom waters of the sedimentation basin. The enrichment coefficients of trace elements in the black shales are revised and an explanation is suggested for the genesis of the rocks with regard for unusual climatic changes.  相似文献   

Field Meeting of the International Subcommission on Carboniferous Stratigraphy “The Historical Type Sections,Proposed and Potential GSSP of the Carboniferous in Russia”, August 11–18, 2009     

A. S. Alekseev  N. V. Goreva 《Stratigraphy and Geological Correlation》2010,18(5):555-559

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Upper carboniferous conodont zones of Russia and their global correlation     

N. V. Goreva  A. S. Alekseev 《Stratigraphy and Geological Correlation》2010,18(6):593-606

The last decade has been marked by significant progress in the study of the stratigraphic ranges of the conodonts characteristic of the Kasimovian and Gzhelian stages in shallow-water sediments of the type sections in the Moscow Basin and the deeper facies of the South Urals. This paper discusses the history of studies of the Upper Carboniferous conodont zonation in Russia and abroad, and proposes a refined zonal conodont scale for the Kasimovian and Gzhelian stages, which may be included, as a standard, into the general Carboniferous scale of Russia. In this scale, the Kasimovian and Gzhelian stages correspond respectively to six (subexcelsus, makhlinae, sagittalis, cancellosus, toretzianus, firmus) and five (simulator, vitali, virgilicus, bellus, wabaunsensis) zones. The proposed scale works for the entire East European Platform and the Urals from the Novaya Zemlya Archipelago in the north to the Mugodzhary Mountains in the south. These regions of Russia are occupied by Upper Carboniferous marine facies. At several levels (especially in the Gzhelian Stage), the scale reliably correlates with zones of the Missourian and Virgilian stages in North America and also Dalaun and Mapingian stages in China.  相似文献   

Long-Term Correlation Between the Nao and Solar Activity     

Renata Lukianova  Genrich Alekseev 《Solar physics》2004,224(1-2):445-454

We extend the correlation analysis of solar signals and the North Atlantic Oscillation (NAO) back in time by using the aa index (since 1868) and the PC index (since 1948) as a proxy of the solar wind energy imparted to the magnetosphere. Prior to the 1940s the records of the NAO and the aa index were not closely connected, while after the 1940s their rhythms matched. We compare two distinctive periods with recent results on the long-scale reconstruction of solar activity. The shift in the NAO–aa interconnection can provide the explanation of a significant increase of solar activity after the 1940s. A strengthening of the interplanetary magnetic field leads to more intensive variations of the high-latitude ionospheric electric field that influences the atmospheric circulation.  相似文献   

Spottedness of red dwarfs: Zonal spottedness models for 13 stars of the by dra type     

I. Yu. Alekseev  R. E. Gershberg 《Astrophysics》1996,39(1):33-45

A zonal spottedness model proposed and developed by us to represent periodic brightness variations of dwarfs of the BY Dra type is applied to a sample of stars with long sequences of BVRI observations.Translated fromAstrofizika, Vol. 39, No. 1, pp. 67–89, January–March, 1995.  相似文献   

The 2019 Ridgecrest Large Earthquake in Southern California: Studying the Source Formation Based on Geomechanical Modelling     

Bondur  V. G.  Gokhberg  M. B.  Garagash  I. A.  Alekseev  D. A.  Gaponova  E. V. 《Doklady Earth Sciences》2022,502(1-2):41-45

Doklady Earth Sciences - Here we present a simulation of the crust’s stress–strain state in the period prior to the 2019 Ridgecrest (M = 7.1) earthquake in Southern California. In the...  相似文献   

Estimation of the effect of protective piers on wind wave parameters in the Sevastopol Bay     

D. V. Alekseev  V. A. Ivanov  E. V. Ivancha  V. V. Fomin  L. V. Cherkesov 《Russian Meteorology and Hydrology》2013,38(4):248-255

An effectiveness of the storm wave attenuation by protective piers in the Sevastopol Bay of the Black Sea is studied on the basis of numerical simulation using the SWAN spectral model. Analyzed are the parameters of waves generated by winds of four main directions as well as by the southern cyclone during the storm on November 11, 2007. It is obtained that waves from the northwest part of the Black Sea penetrate most intensively into the Sevastopol Bay in case of western wind and, to a lesser degree, in case of northern and southern winds. A protective effect of the piers is observed in the west part of the bay only and the wave attenuation near the southern coast is more significant than near the northern one. The area of the southern coast directly behind the southern pier is completely protected from the storm waves and, as moving away from the pier, the danger of intensive wave effect on the coast is kept.  相似文献