Polarization of Evolved Stars Envelopes     

C. Kahane  E. Viard  F. Ménard  P. Bastien  N. Manset 《Astrophysics and Space Science》1997,251(1-2):223-226

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Direct generation of solar and stellar radio bursts by energetic electron maser     

P. Louarn  D. Le Quéau  A. Roux 《Solar physics》1987,111(1):201-206

A fully relativistic electron maser is proposed for the explanation of certain non-thermal solar and stellar radio bursts. This mechanism (maser synchrotron) is based on a gyroresonant interaction between waves and electrons of high energies and uses the free energy contained in an electronic distribution function that peaks for energies around 1 MeV.By a calculation of the growth rates of the three electromagnetic modes, we show that the X-mode prevails for values of _p/ _cup to 2 or 3. This result is very different from the standard cyclotron maser case where such values of _p/ _clead to quench the X-mode growth. Hence, the synchrotron maser instability appears to be a direct and efficient amplification process for considerably larger physical conditions than the cyclotron maser. In addition, the radiation, emitted over the second gyroharmonic, freely propagates without a strong reabsorbtion at the 2 _clayer. All these points can constitute major advantages of this mechanism in an astrophysical context.Proceedings of the Second CESRA Workshop on Particle Acceleration and Trapping in Solar Flares, held at Aubigny-sur-Nère (France), 23–26 June, 1986.  相似文献   

Secular resonances: New results     

Ch. Froeschlé  H. Scholl 《Celestial Mechanics and Dynamical Astronomy》1987,43(1-4):113-117

We integrated numerically, in the frame of the four body problem Sun-Jupiter-Saturn-asteroid the orbit of the asteroid 1974 MA, an Earth-crosser, which is located in a region where three resonances overlap: the two secular resonances ₅ and ₁₆ and the mean motion resonance 5/1. The numerical integration yields a qualitative orbital evolution of this particular region.  相似文献   

Deceleration in the Earth's rotation due to the Sun     

Milan Burša 《Studia Geophysica et Geodaetica》1991,35(3):145-150

Summary The estimate of the tidal long-term decrease in the angular velocity of the Earth's rotation due to the Sun is given as –(0.8±0.3)×10 ^–22 rad s ^–2. It was computed on the basis of the observed total long-term decrease in , of the observed tidal deceleration of the Moon and the observed decrease in the second-degree zonal Stokes geopotential harmonic term. Adopting the estimate given, the product of the Love number and the tidal phase lag angle due to the Sun (in degrees) comes out as 0.53±0.20.

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am a z nuuu u z mu au u, az : –(0,8±0,3) 10 ^–22 a¶rt; ^–2 . ¶rt; ua n a¶rt;a u , n a¶rt;a nuu u ¶rt;z ¶rt;uu u n a¶rt;a u mz az znmuaz naama ma. u num n au, m nu¶rt;u ua a a z u ( za¶rt;a) a z nuua a (0,53±0,20).

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On the detailed magnetostratigraphy of greigite — (Smythite) mineralization,Sokolov Brown-Coal Basin,bohemia     

Miroslav Krs  Marta Krsová  Petr Pruner  Lada Kouklíková 《Studia Geophysica et Geodaetica》1991,35(4):267-284

Summary In the Middle Miocene claystones containing fossil micro-organic matter and overlying the brown-coal seams in the Jii quarry of the Sokolov Brown-Coal Basin, a strongly magnetic layer was found and subjected to detailed palaeomagnetic investigations. The principal carrier of magnetism in this bed (called Kocián's bed) is the ferrimagnetic mineralization of greigite or greigitesmythite showing pronounced metastable properties. This mineralization must be treated with caution during laboratory tests aimed at deriving palaeomagnetic directions. In Kocián's bed, about two metres thick, two zones of palaeomagnetic field transition were identified. The high degree of demagnetization achieved by using thermal stepwise procedures and a MAVACS apparatus enabled the origin of the self-reversal of remanence to be defined after heating to 360°C. The process of chemo-remanent magnetization of the authigenic greigite-(smythite) mineralization fossilizing the palaeomagnetic field was relatively fast; the transition of the palaeomagnetic field is recorded in layers not exceeding a thickness of 2 × 10^–2 m.Presented at 2nd conference on New Trends in Geomagnetism, Castle of Bechyn, Czechoslovakia, September 24–29, 1990.  相似文献   

Tidal contribution of the satellites to removing the angular momentum of Jupiter     

M. Burša 《Studia Geophysica et Geodaetica》1991,35(2):61-74

Summary It has been shown that dynamically, on the basis of the distribution of angular momenta, the Jovian system cannot be considered an analogue within the Solar system. The total tidal decrease in the angular momentum of Jupiter and in its angular velocity of rotation have been estimated, as well as the loss of mechanical energy due to tidal dissipation. It has been concluded that there are no dynamical contradictions with the hypothesis of the common cosmogonic origin of Jupiter and of its eight close satellites.

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aam, m ¶rt;uauu, n an¶rt;u m uma ¶rt;uu, um numa umam aayu um. a a y au ma uma ¶rt;uu numa u z mu z au u—a nuuz mu, ma a nmu au yuu um u—a ¶rt;uunauu. a au, m m ¶rt;uauu azau zunm m zuu aaa numa u z uau u nmu.

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Predicting ground-motion variations at the Turkey-flat test site,California     

J. Zahradník  J. Jech  V. Barták 《Pure and Applied Geophysics》1991,137(1-2):63-84

Results of a single group participating in an international experiment are analyzed. The experiment served to verify computational predictions of the ground-motion variations due to near-surface geological effects at a site established for that purpose by the California Department of Conservation. Based on an acceleration record at a rock location, and geotechnical model of medium, records at the other locations of a nearby sedimentary deposit were predicted. A 2-D finite-difference sensitivity analysis suggested that the lateral wave-propagation effects are negligibly small, and locally 1-D computations are sufficient for the present site. Those computations are compared with observations not available to the authors during the blind prediction. Peak accelerations, peak velocities and RMS accelerations were predicted with errors less than 159%, 114% and 62%, respectively. Maxima of the response spectra were fitted within a factor of 2. The predicted and observed Husid's plots (i.e., the normalized cumulative plots of the acceleration squared) have the correlation coefficients 0.98. The detected misfits do not show any simple relation to the instrument location, component, frequency, or time.  相似文献   

Littoral '92     

H. Flanquart  C. Meur-Férec  Ph. Deboudt  V. Morel  A.-P. Hellequin  et al. 《GeoJournal》1991,24(2):223-223

Reports

Littoral '92  相似文献   

Cosmic-ray propagation in compressible turbulent media     

M. E. Katz  M. Stehlík 《Astrophysics and Space Science》1991,183(2):259-271

The influence of compressibility of media on both the statistical acceleration and the turbulent diffusion of cosmic-ray particles is investigated. The averaging over an ensemble of random velocity fields of the medium was performed in the kinetic equation. The kinetic coefficients, which are responsible for the particle acceleration, were obtained in the cases of weak and strong scattering due inhomogeneous magnetic fields.  相似文献   

A note on the problem of choosing a model of the Universe,IV     

Vladmír Skalský 《Astrophysics and Space Science》1991,181(2):313-322

The Friedmannian model of the Universe with ultra-relativistic equation of statep=–1/3 withk=0 is nondecelerative, i.e., it expands with the constant velocityv=c during the whole expanding phase of evolution of the Universe. The ultrastable nondecelerative model is the only model of the Universe which fulfills all conditions resulting from the quantum-mechanical and relativistic analysis of the Universe.  相似文献