Reply to comments by D. Layzer and J.F. Bedinger on: Turbulence,billows and gravity waves in a high shear region of the upper atmosphere     

K.H. Lloyd  C.H. Low  R.A. Vincent 《Planetary and Space Science》1974,22(3):505

The motion of vapour clouds released into the upper atmosphere appears, in most cases, to be satisfactorily explained by assuming they take up those of the ambient atmosphere, but down-leg releases occasionally show anomalies which have yet to be explained.  相似文献   

Preliminary results of the Apollo 17 infrared scanning radiometer     

W. W. Mendell  F. J. Low 《Earth, Moon, and Planets》1974,9(1-2):97-103

The thermal emission of the lunar surface has been mapped by an infrared scanner from lunar orbit. Samples from approximately 2.5 × 10⁵ scans reveal the full range of lunar temperatures from 80 K to 400 K. The temperature resolution was 1 K with about ± 2 K absolute precision. Spatial resolution was approximately 2 km over most of the horizon-to-horizon scan. The total mapped area amounted to approximately 30% of the lunar surface. The data currently available confirms the large population of nighttime thermal anomalies in western Oceanus Procellarum predicted by Earthbased observations. Most of these ‘hot spots’ are associated with fresh impact features or boulder fields. Also seen in the data are ‘cold spots’ where  相似文献   

Thermospheric observations combining chemical seeding and ground-based techniques—II. Ionospheric drifts and the Sq current system     

D. Rees  G. Haerendel  D.G. Felgate  K.H. Lloyd  C.H. Low 《Planetary and Space Science》1973,21(7):1237-1249

Two Skylark sounding rockets carrying chemical seeding payloads were launched from Woomera, South Australia in October 1969. In conjunction with these firings, the F-region drifts were determined with the Buckland Park aerial array and the results compared with the observed motion of the barium ion clouds. The local ionospheric Sq current system was calculated both from the observed ionospheric parameters and from ground-based magnetograms and the differences between the two results are discussed.  相似文献   

Corrigendum: A well‐established Early–Middle Pleistocene marine sequence on south‐east Zakynthos island,western Greece: magneto‐biostratigraphic constraints and palaeoclimatic implications     

Maria D. Papanikolaou  Maria V. Triantaphyllou  Ellen S. Platzman  Philip L. Gibbard  Conall Mac Niocaill  Martin J. Head 《第四纪科学杂志》2011,26(7):767-767

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基于越南遥感时间序列数据的湄公河三角洲土地利用及河岸变化检测研究   总被引：3，自引：0，他引：3  

阮林道  范巴赫  闵阮青  潘麦黎  蓬晃披 《资源与生态学报(英文版)》2011,(4):370-374

通过采用先进的遥感技术,基于光学和雷达时间序列卫星影像（陆地卫星,SPOT和雷达卫星）,本文对金瓯半岛（位于湄公河三角洲南部）土地覆被变化及湄公河河岸侵蚀情况进行了检测研究。鉴于金瓯半岛典型的土地覆被类型为红树林,通过对1973-2008年红树林遥感影像分析发现,近年来红树林林地面积急剧下降,超过一半的红树林已经转变为虾养殖场。与此同时,检测发现湄公河河岸已经被严重侵蚀,且侵蚀趋势正加速恶化。具体而言,田河和口河的左右两岸被认为是遭受严重侵蚀的热点区域。本文以1966-1968年地形图作为基准线数据,与1989-2009年卫星影像数据进行比照分析,此外采用数字海岸线分析系统（DSAS）模型对未来变化趋势进行了预测。  相似文献   

Reappraisal of the 1982 eruptions of El Chichón Volcano, Chiapas, Mexico: new data from proximal deposits     

J. L. Macías  M. F. Sheridan  J. M. Espíndola 《Bulletin of Volcanology》1997,58(6):459-471

 Additional data from proximal areas enable a reconstruction of the stratigraphy and the eruptive chronology of phases III and IV of the 1982 eruption of El Chichón Volcano. Phase III began on 4 April at 0135 GMT with a powerful hydromagmatic explosion that generated radially fast-moving (∼100 ms^–1) pyroclastic clouds that produced a surge deposit (S1). Due to the sudden reduction in the confining pressure the process continued by tapping of magma from a deeper source, causing a new explosion. The ejected juvenile material mixed with large amounts of fragmented dome and wall rock, which were dispersed laterally in several pulses as lithic-rich block-and-ash flow (F1). Partial evacuation of juvenile material from the magmatic system prompted the entrance of external water to generate a series of hydromagmatic explosions that dispersed moisture-rich surge clouds and small-volume block-and-ash flows (IU) up to distances of 3 km from the crater. The eruption continued by further decompression of the magmatic system, with the ensuing emission of smaller amounts of gas-rich magma which, with the strong erosion of the volcanic conduit, formed a lithic-rich Plinian column that deposited fallout layer B. Associated with the widening of the vent, an increase in the effective density of the uprising column took place, causing its collapse. Block-and-ash flows arising from the column collapse traveled along valleys as a dense laminar flow (F2). In some places, flow regime changes due to topographic obstacles promoted transformation into a turbulent surge (S2) which attained minimum velocities of approximately 77 ms^–1 near the volcano. The process continued with the formation of a new column on 4 April at 1135 GMT (phase IV) that emplaced fall deposit C and was followed by hydromagmatic explosions which produced pyroclastic surges (S3). Received: 13 May 1996 / Accepted: 12 November 1996  相似文献   

ATTITUDES AND ADJUSTMENTS TO THE FLOOD HAZARD IN A MIXED ETHNIC COMMUNITY IN MALACCA TOWN, PENINSULAR MALAYSIA     

Colin H. Leigh  M.A.  Ph.D.  Low Kwai Sim  B.A.  Ph.D. 《Singapore journal of tropical geography》1983,4(1):40-52

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On the presence of electric currents in the solar atmosphere     

M. Hagyard  B. C. Low  E. Tandberg-Hanssen 《Solar physics》1981,73(2):257-268

An elementary analysis based on Ampére's Law is given to separate the general magnetic field above the photosphere into two parts B=B ₁+B ^*. The field B ₁ is a potential field due to electric currents below the photosphere. The field B ^* is produced by electric currents above the photosphere combined with the induced mirror currents. By symmetry, B ^* has a set of field lines lying entirely in the plane z = 0 taken to be the photosphere. This set of field lines can be constructed from given vector magnetograph measurements and represents all the information on the electric currents above the photosphere that a magnetograph can provide. Theoretical illustrations are given and the implications for data analysis are discussed.  相似文献   

On magnetostatic equilibrium in a stratified atmosphere     

B. C. Low 《Solar physics》1980,65(1):147-165

This is a study of the relationship between a magnetic field and its embedding plasma in static equilibrium in a uniform gravity. The ideal gas law is assumed. A system invariant in a given direction is treated first. We show that an exact integral of the equation for force balance across field lines can be derived in a closed form. Using this integral, exact solutions can be generated freely by integrating directly for the distributions of pressure, density and temperature necessary to keep a given magnetic field in equilibrium. Particular solutions are presented for illustration with the solar atmosphere in mind. Extending the treatment to the general system depending on all three spatial coordinates, we arrive at the general form of a theorem of Parker that a magnetic field in static equilibrium must possess certain symmetries. We derive an equation involving the Euler potentials of the magnetic field stipulating these necessary symmetries. Only those magnetic fields satisfying this equation can be in static equilibrium and for these fields, the endowed symmetries make the construction of exact solutions an essentially two dimensional problem as exemplified by the special case of invariance in a given direction.  相似文献   

Stratigraphy, chemistry, and eruptive dynamics of the 12.4 ka plinian eruption of Apoyeque volcano, Managua, Nicaragua     

Denis Ramón Avellán  José Luis Macías  Giovanni Sosa-Ceballos  Gema Velásquez 《Bulletin of Volcanology》2014,76(2):1-19

Apoyeque volcano, located 9 km northwest of Managua city, erupted explosively at 12.4 ka. The Plinian eruption deposited a widespread pumice fall deposit known as the Upper Apoyeque Tephra (UAq). The UAq is massive, reversely graded, and consists of white juvenile pumice (~78 vol.%), a variety of cognate lithics and accidental altered lithics. The whole-rock pumice composition is rhyodacitic (SiO₂?=?66.9–68.5 wt.%) with a mineral paragenesis of plagioclase, orthopyroxene, clinopyroxene, amphibole, titanomagnetite, and ilmenite in a rhyolitic glass groundmass (SiO₂?=?74.4?±?0.6 wt.%). The deposit’s dispersal axis is to the south, with the deposit covering a minimum area of 877 km² within the 50 cm isopach and has a total volume of 3 km³ (dense rock equivalent, 1.15 km³). The eruption column reached a maximum height of ca.28 km. The eruption ejected a total mass of 3?×?10¹² kg at an average rate of 2?×?10⁸ kg/s, and based on available models, we infer duration of almost 4 h. Petrographic and geochemical characteristics suggest that the eruption was triggered by magma mixing.  相似文献