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981.
982.
A large submarine slide on the southern flank of the Bear Island Trough Mouth Fan, southwestern Barents Sea continental slope, has a run-out distance of about 400 km, a total volume of about 1100 km3, and is younger than 330 ka. Three seismic units, comprising mainly hemipelagic sediments has partly filled the slide scar. An increased sedimentation rate on the Bear Island Trough Mouth Fan from Late Pliocene time, probably in combination with abundant earthquakes, is the most likely cause of the slide. Based on these and previous studies, we suggest that large-scale slides were important sediment transport processes during Plio-Pleistocene. 相似文献
983.
Spectroscopic observations in the spectral region 6000–6600 » of major belts and zones of Jupiter have been carried out at Calar Alto Observatory (Spain) during the 1987 opposition, in support to the International Jupiter Watch Program. More than a hundred long-slit, medium resolution spectra have been taken at the coudé focus of the 1.52 m telescope. The longitudinal and latitudinal distribution of the equivalent widths of the methane and ammonia absorption bands at 6190 » and 6450 » have been investigated. Unlike the CH4-6190 » band, the longitudinal distribution in the NH3-6450 » band shows asymmetries in some of the Jovian regions analyzed, being the absorption greater at West than at East limbs. These results are interpreted in terms of inhomogeneous scattering models by the simultaneous variation of the NH3 cloud optical thickness and its altitude level. The north-south scans show little latitudinal dependence on absorption in both methane and ammonia bands, although some relationship could be established between the absorption and relative continuum reflectivity variation.
Also at Departamento de Física Aplicada, Facultad de Ciencias, Universidad de Granada, Campus Universitario Fuentenueva, Granada, Spain. 相似文献
Resumen Se presentan los resultados obtenidos de las observaciones espectroscópicas de las principales zonas y cinturones de Júpiter realizadas durante la oposición de 1987 como una contribución al International Jupiter Watch Program. Las observaciones fueron llevadas a cabo haciendo uso del foco coudé del telescopio de 1.52 m del observatorio hispanoalemán de Calar Alto (España), habiéndose obtenido algo más de cien espectros, de resolución media, en la región espectral de 6000–6600 ». Se exponen los resultados de las anchuras equivalentes de las bandas de absorción del metano en 6190 » y del amoniaco en 6450 », estudiándose, al mismo tiempo, la distribución tanto longitudinal como latitudinal de las mismas. Mientras que los resultados para la banda del metano presentan un comportamiento simétrico en todas las regiones analizadas, las anchuras equivalentes para la banda NH3-6450 » presentan un comportamiento asimétrico en algunas regiones del planeta, con una mayor absorción hacia el limbo del oeste que hacia el del este. Los resultados son interpretados en base a un modelo de scattering no homogéneo, variando, simultáneamente, el espesor óptico y la altitud de la nube de amoniaco. Los espectros tomados en la dirección norte-sur, aunque presentan una dependencia latitudinal pequeña en la absorción de las bandas mencionadas, sugieren una relación entre la absorción y las variaciones de reflectividad en el continuo.
Also at Departamento de Física Aplicada, Facultad de Ciencias, Universidad de Granada, Campus Universitario Fuentenueva, Granada, Spain. 相似文献
984.
C. Debi Prasad T. Chandrasekhar J. N. Desai N. M. Ashok Vinod Krishan 《Journal of Astrophysics and Astronomy》1989,10(1):1-20
During the recent apparition of Comet Halley in 1985-86 a transient ionic event in the form of a blob of H2 O+ emission was recorded in thecoma at ~ 0h UT on 1986 March 13. Observations were carried out using a special IHW filter for H2 O+ emission at 7000 å/175 å, a 35 cm telescope, a Fabry-Perot interferometer and an image intensifier camera from Gurushikhar, Mt Abu. (24?39’N,72? 47’E). A Fabry-Perot inter-ferogram in Ha taken a few minutes later at the same location reveals strong hydrogen emission (Hα) associated with the blob. The velocity field in the blob is structured with relative velocities upto ~ 35km s?1. The event is interpreted as arising due to the sector boundary crossing of the interplanetary magnetic field by the comet 相似文献
985.
K. T. Brazier A. Carramiñana P. M. Chadwick T. R. Currell N. A. Dipper E. W. Lincoln V. G. Mannings T. J. L. McComb K. J. Orford S. M. Rayner K. E. Turver 《Experimental Astronomy》1989,1(2):77-99
The design of very high energy (VHE) gamma ray telescopes is discussed and it is shown that a triple-mirror telescope operating in threefold fast coincidence provides an effective instrument. The design, construction and operation of a large VHE gamma ray telescope with an energy threshold of 300 GeV (at the zenith) and incorporating several novel features is described. The use of a coincidence guard ring technique is shown to result in the rejection of about 50% of the off-source (proton) events which form a high background and limit the sensitivity of such telescopes. 相似文献
986.
Trends in emigration from Ireland over time are reviewed. "During the eighteenth and nineteenth centuries overseas migration to the United States and seasonal harvest migration to Britain were the main types of movement, but over the past 100 years the Irish have developed a special affinity for settling in British towns. Although the outflow was halted for a time during the 1970s, when return migration took over, the 1980s have seen a renewal of the exodus. This time, however, the character of the flow has changed from predominantly low-skill construction and factory workers to embrace better-educated emigrants, including many graduates. This shift reflects Ireland's changing position in the international market for labour." 相似文献
987.
Accurate surface photometry has been obtained inJ andK for 12 giant elliptical galaxies. Ellipses have been fitted, to obtain luminosity, ellipticity, and major axis position angle profiles. The results have been combined with visual profiles from CCD observations. We find that elliptical galaxies become bluer inV - K on the average by 0.3 (mag/sq xr
e) going outward from the nucleus. Radial colour gradients inV - K correlate strongly with those inU - V andB - V. By modelling, using theoretical isochrones, it is found that the observed colour gradients can be explained by a gradient in metallicity, if in addition the proportion of hot stars rises very rapidly with decreasing metallicity. 相似文献
988.
Veeder GJ Hanner MS Matson DL Tedesco EF Lebofsky LA Tokunaga AT 《The Astronomical journal》1989,97(4):1211-1219
We report 10 micrometers infrared photometry for 22 Aten, Apollo, and Amor asteroids. Thermal models are used to derive the corresponding radiometric albedos and diameters. Several of these asteroids appear to have surfaces of relatively high thermal inertia due to the exposure of bare rock or a coarse regolith. The Apollo asteroid 3103, 1982 BB, is recognized as class E. The Jupiter-crossing Amor asteroid 3552, 1983 SA, is confirmed as class D, but low albedos remain rare for near-Earth asteroids. 相似文献
989.
Tōnu Viik 《Astrophysics and Space Science》1992,198(2):265-280
The external field of radiation in Rayleigh-Cabannes atmospheres with constant and linear sources is found using the resolvent matrix approach. If the internal sources are constant the external field may be described by theX-, Y-, andH-matrices. For the case with linear sources we need the derivatives of these matrices with respect to angular variable. The respective scheme for their determination is given.A set of integro-differential equations for theX- andY-matrices is derived and solved numerically. Some relations between the moments of theH-matrix are given and a sample of results for external fields are provided. 相似文献
990.
The Very Large Array (VLA) and the frequency agile interferometer at the Owens Valley Radio Observatory (OVRO) were used to observe the M8.1 flare of 23 June, 1988. The VLA obtained images prior to and during the flare at 333 MHz, and at 1.5 and 4.7 GHz. The frequency agile interferometer at Owens Valley obtained interferometer amplitude and total power spectra of the flare at 45 frequencies between 1 and 18 GHz. The observations were supplemented by radiometer measurements made by the USAF RSTN network site at Palehua, HI, by GOES soft X-ray observations, by USAF SOON H filtergrams, and by a KPNO photospheric magnetogram.The radio data reveal a wide variety of phenomena, including: (i) a multiply impulsive microwave burst that is essentially thermal in character; (ii) stationary discrete components at 1.5 GHz, associated temporally and spatially with distant brightenings in Ha; (iii) a dynamical component at 1.5 GHz associated with hot plasma moving subsonically into the corona; (iv) the appearance of intense, short-lived, decimetric burst activity near the lead sunspot in the active region at 1.5 GHz, indicative of a high degree of inhomogeneity in the source.The unusually complete radio coverage allows us to investigate the transport of energy from the initial site to sites of distant H brightenings. The transport of energy appears to be most consistent with slow, thermal processes, rather than rapid transport by nonthermal electron beams. 相似文献