Spectral Diagnostics of Langmuir Coronal Plasma Turbulence Based on the Radio Emission at the Double Plasma Frequency     

Kudryavtsev  I. V.  Kaltman  T. I. 《Geomagnetism and Aeronomy》2021,61(8):1172-1177

Geomagnetism and Aeronomy - Analysis of the radiation of solar radio bursts with a fine structure generated at a double plasma frequency makes it possible to obtain information on the energy...  相似文献   

Possible Cause of Differences between Reconstructions of the Heliospheric Modulation Potential in the Past Based on Data on the 10Be Content in the Ice of the Antarctic and Greenland     

Kudryavtsev  I. V. 《Geomagnetism and Aeronomy》2021,61(8):1216-1220

Geomagnetism and Aeronomy - The paper presents reconstructions of the heliospheric modulation potential based on data on the content of the cosmogenic isotope 10Be in the ice layers of Antarctica...  相似文献   

Stars with discrepant v sin i as derived from the Ca II λ3933 Å and Mg II λ4481 Å lines. IV. HD8837—a shell star, HD47964 and HD183986—new binaries     

J. Zverko  I. Romanyuk  I. Iliev  D. Kudryavtsev  I. Barzova  E. Semenko  I. Stateva 《Astrophysical Bulletin》2013,68(4):442-453

Axial rotation of a star plays an important role in its evolution, physical conditions in its atmosphere, and appearance of its spectrum. We have analyzed CCD spectra of three stars for which their projected rotational velocity remarkably differs when derived from the Ca II λ 3933 Å and MgII λ 4481 Å lines. We derived effective temperatures and surface gravities using published uvbyβ photometries and computed synthetic spectra. Comparing observed line profiles of the two lines with the computed ones, we estimated values of v sin i. We also derived radial velocities by means of the cross-correlation function. HD8837 is known to be a shell star with pronounced narrow absorption cores in the Balmer lines as well as in the strong metal lines; however, we do not confirm the emission component in the core of Hβ. HD47964 has been discovered by Hipparcos to be a double. However, in our spectra we do not find traces of the other star. Based on the Hipparcos data, we estimated that the other star would be a main sequence A4 star with an extremely high rotational velocity resulting in wiping out any traces of spectral lines of the companion. HD183986 is known to be a triple star. However, we have found a manifestation of a so far not discovered companion of the component HD183986A and estimated it as a main sequence A5 star having v sin i of about 150 km/s.  相似文献   

Spatial brightness distribution of hard X-Ray emission along flare loops     

V. F. Melnikov  Yu. E. Charikov  I. V. Kudryavtsev 《Geomagnetism and Aeronomy》2013,53(7):863-866

The work is devoted to the simulation of recently discovered hard X-ray and gamma radiation sources localized near the top of solar flare loops. The calculations were performed in the context of a model of a flare magnetic loop inhomogeneous with respect to the magnetic field. Two cases of injection were considered: isotropic and anisotropic along the loop axis. The distributions of electrons along the loop are found by solving the nonstationary relativistic kinetic equation in the Fokker-Planck form. Based on the calculated electron distribution functions, the spatial brightness distribution of hard X-ray and gamma radiation has been calculated. Radiation characteristics are compared for different sets of injection parameters.  相似文献   

Reconstructions of the <Superscript>14</Superscript>С cosmogenic isotope content from natural archives after the last glacial termination     

I. V. Kudryavtsev  D. M. Volobuev  V. A. Dergachev  Yu. A. Nagovitsyn  M. G. Ogurtsov 《Geomagnetism and Aeronomy》2016,56(7):858-862

Data on the content of the ¹⁴C cosmogenic isotope in tree rings, which were obtained as a result of laboratory measurements, are often used when solar activity (SA) is reconstructed for previous epochs, in which direct observations are absent. However, these data contain information not only about SA variations but also about changes in the Earth climatic parameters, such as the global temperature and the CO₂ content in the Earth’s atmosphere. The effect of these variations on the ¹⁴C isotope content in different natural reservoirs after the last glacial termination to the middle of the Holocene is considered. The global temperature and the CO₂ content increased on this time interval. In this case the ¹⁴C absolute content in the atmosphere increased on this time interval, even though the ¹⁴С to ¹²С isotope concentration ratio (as described by the Δ¹⁴С parameter) decreased. These variations in the radiocarbon absolute content can be caused by its redistribution between natural reservoirs. It has been indicated that such a redistribution is possible only when the rate of carbon exchange between the ocean and atmosphere depends on temperature. The values of the corresponding temperature coefficient for the 17–10 ka BC time interval, which make it possible to describe the carbon redistribution between the ocean and atmosphere, have been obtained.  相似文献   

Estimating the global flux of methane into the atmosphere and its seasonal variations     

V. V. Adushkin  V. P. Kudryavtsev 《Izvestiya Atmospheric and Oceanic Physics》2013,49(2):128-136

A new method of estimating the global fluxes of methane into the Earth’s atmosphere is proposed. This method allows one to take into account the whole spectrum of methane sources irrespectively of their location and calculate seasonal variations in methane fluxes. The results of numerical calculations of the amount of methane emitted into the atmosphere on the basis of this method are supported by data obtained from field measurements. In the Northern Hemisphere (NH), during fall, maximum concentrations of CH₄ are due to methane sources in the arctic region which have not been taken into account before. For the condition of balance between the emission and sink of methane to be fulfilled, the total capacity of its sources amounts to no less than ～530 Tg/year for the NH and ～470 Tg/year for the Southern Hemisphere (SH). The results of our calculations and an analysis of the behavior of the concentration and mass of methane in the Earth’s hemispheres show that the global flux of methane from the surfaces of the lithosphere and ocean into the atmosphere may amount to more than ～1000 Tg/year.  相似文献   

Note on the Growth Rate of Water Waves Propagating at an Arbitrary Angle to the Wind     

J. F. Meirink  V. K. Makin  V. N. Kudryavtsev 《Boundary-Layer Meteorology》2003,106(1):171-183

The dependence of the turbulent airflow over water waves on the angle,, between mean wind and wavedirections is investigated. To this end,an existing semi-analytical model is extended. In this model, the main simplification of the problem is obtained by using the well-established divisionof the wave boundary layer into inner and outer regions for modelling turbulence. The effect of waves on turbulence is restricted to the thin inner region. Simulations show that the influence of the wind speed component transverse to the wave direction on the air flow, and hence on the growth rate of the waves, is small. This is confirmed by calculations with a numerical model that solves the full Reynolds equations using a second-order turbulence closure scheme. The growth rate of slowly moving waves (as compared to the wind speed) is then proportional to cos², whereas, for faster waves, it has a narrower angular distribution.  相似文献   

Erratum: “A Study of rare-earth elements in the atmospheres of chemically peculiar stars. Pr III and Nd III lines” [Astronomy Reports 45, 382–388 (2001)]     

T. A. Ryabchikova  I. S. Savanov  V. P. Malanushenko  D. O. Kudryavtsev 《Astronomy Reports》2002,46(8):696

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Microvariability of line profiles in the spectra of OB stars: III. The supergiant ρ LEO     

A. F. Kholtygin  S. N. Fabrika  T. E. Burlakova  G. G. Valyavin  G. A. Chuntonov  D. O. Kudryavtsev  D. Kang  M. V. Yushkin  G. A. Galazutdinov 《Astronomy Reports》2007,51(11):920-931

We observed the bright supergiant ρ Leo (B1 lab) in January–February 2004 using the 6-m telescope of the Special Astrophysical Observatory (Russia) and the 1.8-m telescope of the Bohyunsan Optical Astronomy Observatory (South Korea). 47 spectra with high time resolution (4–10 min), signal-to-noise ratios 300–1000, and spectral resolutions 45 000–60 000 were obtained. We detected variability in the HeI, SiII, SiIII, and NII line profiles, which may be due to rotational modulation of the profiles and photospheric pulsations of ρ Leo. The possible influence of the stellar magnetic field on the line-profile variations is discussed.  相似文献   

Aerodynamic roughness of the sea surface at high winds   总被引：2，自引：0，他引：2  

Vladimir N. Kudryavtsev  Vladimir K. Makin 《Boundary-Layer Meteorology》2007,125(2):289-303

The role of the surface roughness in the formation of the aerodynamic friction of the water surface at high wind speeds is investigated. The study is based on a wind-over-waves coupling theory. In this theory waves provide the surface friction velocity through the form drag, while the energy input from the wind to waves depends on the friction velocity and the wind speed. The wind-over-waves coupling model is extended to high wind speeds taking into account the effect of sheltering of the short wind waves by the air-flow separation from breaking crests of longer waves. It is suggested that the momentum and energy flux from the wind to short waves locally vanishes if they are trapped into the separation bubble of breaking longer waves. At short fetches, typical for laboratory conditions, and strong winds the steep dominant wind waves break frequently and provide the major part of the total form drag through the air-flow separation from breaking crests, and the effect of short waves on the sea drag is suppressed. In this case the dependence of the drag coefficient on the wind speed is much weaker than would be expected from the standard parameterization of the roughness parameter through the Charnock relation. At long fetches, typical for the field, waves in the spectral peak break rarely and their contribution to the air-flow separation is weak. In this case the surface form drag is determined predominantly by the air-flow separation from breaking of the equilibrium range waves. As found at high wind speeds up to 60 m s⁻¹ the modelled aerodynamic roughness is consistent with the Charnock relation, i.e. there is no saturation of the sea drag. Unlike the aerodynamic roughness, the geometrical surface roughness (height of short waves) could be saturated or even suppressed when the wind speed exceeds 30 m s⁻¹.  相似文献