Nitric acid vapour measurements in the troposphere and lower stratosphere by chemical ionisation mass spectrometry     

G. Knop  F. Arnold 《Planetary and Space Science》1985,33(8):983-986

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Anomalies of some tidal waves of UT1   总被引：1，自引：0，他引：1  

N. Capitaine  B. Guinot 《Geophysical Journal International》1985,81(3):563-568

Summary. The M _f and M _m waves of UT1 have been analysed from the BIH data during the period 1967.0 to 1984.0 in order to derive the Love number k .
These analyses performed during successive intervals of this period show some anomalies in the values of the Love number k derived from the M _f wave. Large variations with time of the amplitude and the phase appear for this wave while the values derived from the M _m wave present a good stability during the whole period.
The spectrum of the UT1-residuals (as obtained by removing the theoretical zonal tidal UT1 terms) shows the existence of a perturbation wave near the M _f period. This wave lies in the range 13.5–13.9 day according to the analysed interval; it could be related with the perturbation wave noticed by some authors near the M _f gravimetric wave.  相似文献   

Spectra of simulated lightning on Venus,Jupiter, and Titan     

W.J. Borucki  R.L. Mc Kenzie  C.P. McKay  N.D. Duong  D.S. Boac 《Icarus》1985,64(2):221-232

Laser-induced plasmas in various gas mixtures were used to simulate lightning in other planetary atmospheres. This method of simulation has the advantage of producing short-duration, high-temperature plasmas free from electrode contamination. The laser-induced plasma discharges in air are shown to accurately simulate terrestrial lightning and can be expected to simulate lightning spectra in other planetary atmospheres. Spectra from 240 to 880 nm are presented for simulated lightning in the atmospheres of Venus, Earth, Jupiter, and Titan. The spectra of lightning on the other giant planets are expected to be similar to that of Jupiter because the atmospheres of these planets are composed mainly of hydrogen and helium. The spectra of Venus and Titan show substantial amounts of radiation due to the presence of carbon atoms and ions and show CN Violet radiation. Although small amounts of CH₄ and NH₃ are present in the Jovian atmosphere, only emission from hydrogen and helium is observed. Most differences in the spectra can be understood in terms of the elemental ratios of the gas mixtures. Consequently, observations of the spectra of lightning on other planets should provide in situ estimates of the atmospheric and aerosol composition in the cloud layers in which lightning is occuring. In particular, the detection of inert gases such as helium should be possible and the relative abundance of these gases compared to major constituents might be determined.  相似文献   

Results of Photometric and Polarimetric Observations of the Fuor V1057 Cyg from the Time of an Outburst to the Present     

E. N. Kopatskaya  V. P. Grinin  D. N. Shakhovskoi  O. S. Shulov 《Astrophysics》2002,45(2):143-149

Observations of the brightness, color, and polarization of the fuor V1057 Cyg over more than 30 years are presented and briefly discussed. Variability of the linear polarization was found.  相似文献   

CCD photometry inVRI bands of the galactic cluster NGC 2818     

R. Surendiranath  N. Kameswara Rao  Ram Sagar  J. S. Nathan  K. K. Ghosh 《Journal of Astrophysics and Astronomy》1990,11(2):151-166

bdAbstract The open cluster NGC 2818 containing a planetary nebula has been observed inVRI bands using the CCD system at prime focus of the 2.3-metre Vainu Bappu Telescope. The study extending to starsV ∼ 21 magnitude establishes the distance modulus as(m-M) ₀ = 12.9 ±0.1 for the cluster. Based on the fitting of theoretical isochrones computed for solar metallicity, an age of 5(±1) × 10₈ years has been assigned to the cluster. Association of the planetary nebula with the cluster indicates that the progenitor mass of the planetary nebula on the main sequence is ≥2.5M_⊙ Based on observations obtained with the Vainu Bappu Telescope.  相似文献   

Variable sources in BL Lac objects: Energy distribution in the optical range deduced from multicolor photometry     

V. A. Gagen-Torn  S. G. Marchenko  O. B. Mikolaichuk 《Astrophysics》1990,32(3):244-251

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Sonar cross sections of bodies partially insonified by finite sound beams     

Gaunaurd  G. 《Oceanic Engineering, IEEE Journal of》1985,10(3):213-230

An object that is partially insonified by a collimated sound beam may have a scattering cross section sometimes much larger than when the object is totally covered by the incident beam. We quantitatively study this partial insonification problem here, under the classical method of physical optics. The importance of this study stems from the fact that partial coverage of the target by the beam is the situation most likely to occur in many cases of practical importance. We consider several basic target shapes partially insonified by finite beams. These shapes include the spherical, the infinite and finite cylinder, the flat plate, and the capped sphere. High-frequency approximations of the resulting integrals, obtained by means of the saddle-point method, show the relative importance of the scattering centers located at the beam's specular reflection points, or at the edges of the spots that the beam shines on the scatterers. The physical-optics method is extended to obtain formulas for the bistatic cross sections of partially insonified objects. The results are numerically evaluated and graphically displayed in many pertinent instances and compared to the predictions of approaches, such as the Fresnel-zones method and the Geometrical Theory of Diffraction (GTD). The predictions of the physical-optics method have all the advantages and deficiencies of this method and, with very minor modifications, hold equally well for the partial illumination of objects by beams of electromagnetic radiation.  相似文献   

Small-scale mantle flows and induced lithospheric stress near island arcs     

Steven N. Ward 《Geophysical Journal International》1985,81(2):409-428

Summary. This paper explores the middle ground between complex thermally-coupled viscous flow models and simple corner flow models of island arc environments. The calculation retains the density-driven nature of convection and relaxes the geometrical constraints of corner flow, yet still provides semianalytical solutions for velocity and stress. A novel aspect of the procedure is its allowance for a coupled elastic lithosphere on top of a Newtonian viscous mantle. Initially, simple box-like density drivers illustrate how vertical and horizontal forces are transmitted through the mantle and how the lithosphere responds by trench formation. The flexural strength of the lithosphere spatially broadens the surface topography and gravity anomalies relative to the functional form of the vertical flow stresses applied to the plate base. I find that drivers in the form of inclined subducting slabs cannot induce self-driven parallel flow; however, the necessary flow can be provided by supplying a basal drag of 1–5 MPa to the mantle from the oceanic lithosphere. These basal drag forces create regional lithospheric stress and they should be quantifiable through seismic observations of the neutral surface. The existence of a shallow elevated phase transition is suggested in two slab models of 300 km length where a maximum excess density of 0.2 g cm⁻³ was needed to generate an acceptable mantle flow. A North New Hebrides subduction model which satisfies flow requirements and reproduces general features of topography and gravity contains a high shear stress zone (75 MPa) around the upper slab surface to a depth of 150 km and a deviatoric tensional stress in the back arc to a depth of 70 km. The lithospheric stress state of this model suggests that slab detachment is possible through whole plate fracture.  相似文献   

Optimal Filtering Algorithm for Stochastic 2-D FMM Ⅱ with Multiplicative Noise     

CHUDongsheng LIANGMeng SHIXin ZHANGLing 《中国海洋大学学报(英文版)》2004,3(1):106-110

1　Introduction　Inrecentyearstherehasbeengrowingresearchin terestinthetwo dimensional (2 D )systemtheory .The 2 Dsystemsmayfindapplicationsinareassuchasmarineseismicdataprocessingandimageprocessing .Althoughmoreandmorevaluableresultshavebeengained ,mos…  相似文献   

Periodicity in spectral variations of IC 4997?     

G. A. Gurzadyan 《Astrophysics and Space Science》1992,193(1):105-107

The emission lines in the spectra of some planetary nebula experience variations with the time. These variations (due to evolution effects and by their nature) differ from the spectral changes which we usually observe in stars. It appears that the long-scale and systematic observations on the intensity behaviour of different emission lines of nebula may be used as an independent indicator to receive a principally new and quite unpredicted category of information related to the physics of nebulae and their nuclei. Particularly, the analysis of long standing observations carried out in relation to the forbidden lines 4363 [Oiii] andN ₁+N ₂ [Oiii] of double-ionized oxygen lead to a conception about the possible existence ofrelativistic electrons of moderate energy in planetary nebulae and the generation oftransition radiation as a result of electrodynamic interaction of these electrons with the dust particles in nebula (Gurzadyan, 1991). Just on the basis of the same observational material, the long-scale periodicity in the activity or variations of a star-like planetary nebula IC 4997 is discovered about which is the present note.  相似文献