Minor constituents in the Martian atmosphere from the ISM/Phobos experiment     

Rosenqvist J  Drossart P  Combes M  Encrenaz T  Lellouch E  Bibring JP  Erard S  Langevin Y  Chassefiere E 《Icarus》1992,98(2):254-270

Global Martian atmospheric results derived from the infrared imaging spectrometer ISM flown aboard the Phobos 2 Soviet spacecraft are presented. Over low altitude regions the expected CO mixing ratio of (8 +/- 3) x 10(-4) is measured. Variations of the 2.35-micrometers feature are inconsistent with this value over the Great Martian Volcanoes. If the 2.35-micrometers band is entirely attributable to carbon monoxide, the CO mixing ratio is typically depleted by a factor of 3 over these high altitude areas. Orography should play a major role in the existence of this CO "hole." If, however, these spectral variations at 2.35 micrometers are due to the surface composition, the fraction of the surface covered by the responsible mineral must smoothly decrease as the surface elevation decreases. This phenomenon implies a strong interaction between the surface and the atmosphere for the Great Martian Volcanoes. Diurnal behavior and latitudinal variations of water vapor are globally consistent with Viking measurements. During the Phobos observations, the water vapor amounts over the bright equatorial regions range around 11 pr-micrometers during the day. These amounts are slightly larger than those inferred from 1976 to 1979. The lack of global dust storms during 1988-1989 could explain the enhancement of H2O in the atmosphere.  相似文献   

The dust distribution within the inner coma of comet P/Halley 1982i: encounter by Giotto's impact detectors     

McDonnell JA  Alexander WM  Burton WM  Bussoletti E  Evans GC  Evans ST  Firth JG  Grard RJ  Green SF  Grun E  Hanner MS  Hughes DW  Igenbergs E  Kissel J  Kuczera H  Lindblad BA  Langevin Y  Mandeville JC  Nappo S  Pankiewicz GS  Perry CH  Schwehm GH  Sekanina Z  Stevenson TJ  Zarnecki JC et AL 《Astronomy and Astrophysics》1987,187(1-2):719-741

Analysis of the data from Giotto's Dust Impact Detection System experiment (DIDSY) is presented. These data represent measurement of the size of dust grains incident on the Giotto dust shield along its trajectory through the coma of comet P/Halley on 1986 March 13/14. First detection occurred at some 287000 km distance from the nucleus on the inbound leg; the majority of the DIDSY subsystems remained operational after closest approach (604 km) yielding the last detection at about 202000 km from the nucleus. In order to improve the data coverage (and especially for the smallest grains, to approximately 10(-19) kg particle mass), data from the PIA instrument has been combined with DIDSY data. Flux profiles are presented for the various mass channels showing, to a first approximation, a 1/R2 flux dependence, where R is the distance of the detection point from the cometary nucleus, although significant differences are noted. Deviations from this dependence are observed, particularly close to the nucleus. From the flux profiles, mass and geometrical area distributions for the dust grains are derived for the trajectory through the coma. Groundbased CCD imaging of the dust continuum in the inner coma at the time of encounter is also used to derive the area of grains intercepted by Giotto. The results are consistent with the area functions derived by Giotto data and the low albedo of the grains deduced from infrared emission. For the close encounter period (-5 min to +5 min), the cumulative mass distribution function has been investigated, initially in 20 second periods; there is strong evidence from the data for a steepening of the index of the mass distribution for masses greater than 10(-13) kg during passage through dust jets which is not within the error limits of statistical uncertainty. The fluences for dust grains along the entire trajectory is calculated; it is found that extrapolation of the spectrum determined at intermediate masses (cumulative mass index alpha = 0.85) is not able to account for the spacecraft deceleration as observed by the Giotto Radio Science Experiment and by ESOC tracking operations. Data at large masses (>10(-8) kg) recently analysed from the DIDSY data set show clear evidence of a decrease in the mass distribution index at these masses within the coma, and it is shown that such a value of the mass index can provide sufficient mass for consistency with the observed deceleration. The total particulate mass output from the nucleus of comet P/Halley at the time of encounter would be dependent on the maximum mass emitted if this change in slope observed in the coma were also applicable to the emission from the nucleus; this matter is discussed in the text. The flux time profiles have been converted through a simple approach to modeling of the particle trajectories to yield an indication of nucleus surface activity. There is indication of an enhancement in flux at t approximately -29 s corresponding to crossing of the dawn terminator, but the flux detected prior to crossing of the dawn terminator is shown to be higher than predicted by simple modelling. Further enhancements corresponding to jet activity are detected around +190 s and +270 s.  相似文献   

Simultaneous multifrequency observations of Markarian 421     

Brodie J  Bowyer S  Tennant A 《The Astrophysical journal》1987,318(1):175-187

The highly variable BL Lacertae object Mrk 421 has been observed simultaneously in the radio, optical ultraviolet, and X-ray bands over a period of 4 days in early 1984 December and once again in early 1985 January. Using the EXOSAT observatory, we found that dramatic changes occurred in the X-ray flux on a time scale of less than a mouth. During this time the 2-10 keV flux dropped by a factor of 8, whereas the 0.1-1 keV flux decreased by a factor of only 2. These changes were not reproduced at longer wavelengths during the period of simultaneous observations. However, a drop in the ultraviolet flux occurred some months later, which is consistent with the longer characteristic loss times for the lower energy electrons. Since the ultraviolet through radio flux is stable when the X-ray flux is changing, it is extremely unlikely that a simple synchrotron model can account for the full spectrum; in this model the whole spectrum is expected to rise uniformly and in phase as a result of the injection of energetic particles. A simple synchroton self-Compton model that is self-absorbed in the radio also requires an X-ray flux which is many orders of magnitude greater than is observed. However, this discrepancy may be explained by relativistic beaming of electrons with delta > approximately 40 or by a model in which the self-absorption turnover occurs in the optical, and the synchrotron break occurs in the X-rays. Shorter time scale (approximately 10,000 s) variability was also apparent in the 2-10 keV X-ray light curves, and we suggest that it may be a direct measure of the injection time scale. Although reasonable fits resulted when the X-ray data were compared with a simple power-law model with some absorption, a substantial improvement in chi 2 was obtained by adding a high-energy exponential cutoff. Use of this model produced a spectral index close to that typically found in the optical for BL Lacertae objects, in contrast to the high values usually inferred from X-ray spectra.  相似文献   

Recent population trends in the Swiss Alps     

Billet J  Rougier H 《Revue de géographie alpine / publieé par l'Institute de géographie alpine (Université de Grenoble)》1984,72(1):9-20

Recent demographic trends in the Alpine areas of Switzerland are examined. Areas of population loss and gain are identified, and the importance of tourism for areas experiencing population growth is established. Efforts to support the demographic and economic viability of mountain areas are described.  相似文献   

The space-time and systematic concepts in regional planning: the population aspect     

Uyanga J 《The Indonesian journal of geography》1984,14(47):9-18

"The paper contends that it is possible to synthesise the various studies unilineally relating population processes to regional development into a comprehensive overview within which the process of differential regional development and planning and that of differential population levels can be universally assessed in a system framework. The paper presents a simple planning control system model of regional development based on its process and structure in space and the dynamics of population reactions over time."  相似文献   

Proton production in relativistic heavy ion collisions; comparison with a thermodynamical model     

Parizet MJ  Alard JP  Rahmani A  Montarou G  Augerat J  Bastid N  Demaison P  Dupieux P  Fraysse L  Marroncle J 《International journal of modern physics. A, Particles and fields, gravitation, cosmology》1989,4(14):3689-3703

Experimental results concerning proton production in nuclear collisions, obtained at Saturne with the Diogene 4 pi facility, are compared with the predictions of a thermodynamical model, using collective velocity distributions combined with a statistical thermodynamics in local rest frames. Experimental differential cross sections for alpha + nucleus and Neon + nucleus central collisions at incident energies between 200 and 800 MeV per nucleon are well reproduced by the model, for an angular range 30-110 degrees in the laboratory system. Extracted values of the temperatures are compared with those given by other authors.  相似文献   

The Soviet Far East: a report on urban and rural settlement and population change, 1966-1989     

Sallnow J 《Soviet geography》1989,30(9):670-683

"This article provides a general overview of trends in urban-rural population change and evolution of the settlement system in the Soviet Far East since 1966, incorporating data published in the recent national statistical yearbooks and the preliminary 1989 census report....Total population in the Soviet Far East increased from 5,435,000 in 1966 to 7,941,000 by January 12, 1989, with the share of the urban population now comprising over three-quarters of the total. Migration patterns into and out of the region are discussed and cities planned for expansion are identified."  相似文献   

TriNet：南加利福尼亚的地震和强震记录     

赵新平 Mori  J 《地震科技情报》2000,(4):27-28

  相似文献   

对历史地震的新见解     

魏爱莲  张德成 《地震科技情报》1998,(2):30-32

  相似文献   

雪峰金矿田矿床地质特征及成矿模式     

彭小军  ;廖秋明  ;吴跃升  ;魏道芳  ;刘学通 《湖南地质》2008,(4):35-39

雪峰金矿田位于扬子准地台与华南加里东褶皱带两大地构造单元过渡地带的巨型雪峰弧形推覆剪切金锑钨成矿带中段西部，被两条深大断裂及三大岩体所夹持，具有地层-构造-岩浆岩三位一体的极好成矿条件。区内地壳运动频繁，赋矿地层发育，地质构造复杂，岩浆活动强烈，金矿床点星罗棋布，由金矿化和围岩蚀变引起的物化探异常面积大、强度高、浓集中心明显，遥感地质环形构造及线性构造十分发育。矿体赋存于震旦系长滩组和前震旦系芙蓉溪群陆源碎屑及火山碎屑沉积浅变质岩的北东、北西向韧性、张扭性含金剪切断裂蚀变带及砂岩层中垂直层理的张扭性裂隙、顺层节理、片理和板岩层间剥离带、层间断层和层内裂隙中。矿床具成矿物质多来源，成矿过程多期、多阶段、多成因和多次叠加与再造成矿特点，形成韧性含金剪切带型、砂岩细脉浸染型和石英脉型复成金矿床。矿田中大型矿床1处，中、小型矿床多处，初步查明金金属量D＋E＋333近100t。研究认为矿田找矿潜力巨大，是个不可多得的超大型金矿成矿区。  相似文献