Transport Characteristics of the Near-Surface Layer of the Nucleus of Comet 67P/Churyumov–Gerasimenko     

Reshetnyk  V.  Skorov  Yu.  Vasyuta  M.  Bentley  M.  Rezac  L.  Agarwal  J.  Blum  J. 《Solar System Research》2021,55(2):106-123

Solar System Research - The paper considers the free molecular flow of gas through the dusty porous surface layer of a comet nucleus. The study is based on computer models of generation of a porous...  相似文献   

Magnetic Activity Associated With Radio Noise Storms     

Bentley  R.D.  Klein  K.-L.  van Driel-Gesztelyi  L.  Démoulin  P.  Trottet  G.  Tassetto  P.  Marty  G. 《Solar physics》2000,193(1-2):227-245

As it crossed the solar disk in May and June 1998, AR 8227 was tracked by TRACE, Yohkoh, SOHO, and many ground-based observatories. We have studied how the evolution of the magnetic field resulted in changes in activity in the corona. In particular, we examine how the evolving field may have led to the acceleration of electrons which emit noise storms observed by the Nançay Radio Heliograph between 30 May and 1 June 1998, in the absence of any flare. The magnetic changes were related to moving magnetic features (MMFs) in the vicinity of the leading spot and are related to the decay of this spot. Within the limits of the instrumental capabilities, the location in time and space of the radio emissions followed the changes observed in the photospheric magnetograms. We have extrapolated the photospheric magnetic field with a linear force-free approximation and find that the active region magnetic field was very close to being potential. These computations show a complex magnetic topology associated to the MMFs. The observed photospheric evolution is expected to drive magnetic reconnection in such complex magnetic topology. We therefore propose that the MMFs are at the origin of the observed metric noise-storms.  相似文献   

Groundwater flow and storage processes in an inactive rock glacier          下载免费PDF全文

Jordan S. Harrington  Alexandra Mozil  Masaki Hayashi  Laurence R. Bentley 《水文研究》2018,32(20):3070-3088

Groundwater flow through coarse blocky landforms contributes to streamflow in mountain watersheds, yet its role in the alpine hydrologic cycle has received relatively little attention. This study examines the internal structure and hydrogeological characteristics of an inactive rock glacier in the Canadian Rockies using geophysical imaging techniques, analysis of the discharge hydrograph of the spring draining the rock glacier, and chemical and stable isotopic compositions of source waters. The results show that the coarse blocky sediments forming the rock glacier allow the rapid infiltration of snowmelt and rain water to an unconfined aquifer above the bedrock surface. The water flowing through the aquifer is eventually routed via an internal channel parallel to the front of the rock glacier to a spring, which provides baseflow to a headwater stream designated as a critical habitat for an at‐risk cold‐water fish species. Discharge from the rock glacier spring contributes up to 50% of basin streamflow during summer baseflow periods and up to 100% of basin streamflow over winter, despite draining less than 20% of the watershed area. The rock glacier contains patches of ground ice even though it may have been inactive for thousands of years, suggesting the resiliency of the ground thermal regime under a warming climate.  相似文献   

Hydrogeological implications of paleo-fluvial architecture for the Paskapoo Formation, SW Alberta, Canada: a stochastic analysis     

Erick R. Burns  Laurence R. Bentley  Masaki Hayashi  Stephen E. Grasby  Anthony P. Hamblin  Derald G. Smith  Paul R. J. Wozniak 《Hydrogeology Journal》2010,18(6):1375-1390

Fluvial systems tend to deposit sediment in well-defined relational geometries and in vertically and laterally repeating patterns. These sedimentary deposits are preserved to varying degrees depending on how much the fluvial system reworks the deposits. The Paskapoo bedrock aquifer system in southern Alberta, Canada, was deposited in a foreland depositional basin during uplift of the Rocky Mountains, and both the geomorphic model and field evidence indicate that the upper 100 m of the local aquifer system contains well-preserved, highly connected paleo-channels and associated overbank deposits. In order to evaluate the value of different types of data, a simplified stochastic-numerical groundwater flow model was developed to examine the sensitivity of results to model parameters. Parameters examined include: fraction of the formation made up of channel sands; meander and sinuosity factors; width-to-depth ratios of preserved channels; and crevasse splay conductivity. In all cases examined, the system exhibited anisotropic behavior with the along-channel flow direction being the most permeable and the vertical direction being least permeable. In general, the strongest control on the resulting effective anisotropic hydraulic conductivities was channel fraction, but geometric factors that control between-channel connectivity (e.g., channel sinuosity) had an appreciable effect on the across-channel flow direction effective permeability.  相似文献   

Environmental influences on the formation of sedimentary fabric in a fine-grained carbonate-shelf environment: Dry Tortugas, Florida Keys     

S. J. Bentley  C. A. Nittrouer 《Geo-Marine Letters》1997,17(4):268-275

 Sedimentological studies were undertaken in the Dry Tortugas to examine environmental influences on the formation of sedimentary fabric. ²³⁴Th, ²¹⁰Pb, grain size, porosity, and fabric analyses reveal the presence of a soft, fine-grained, well mixed surface layer underlain by compact, shelly, intensely bioturbated carbonate muds. Vertical zonation of biogenic structures indicates that deep bioturbation is advective and results in transport of fine material to the seabed surface. The impact of physical oceanographic processes appears to be restricted to the surface layer; however, potential for preservation of this layer in the sediment record is low due to intense mixing in deeper sediments. Thus, preserved sediments retain an incomplete record of the dominant benthic processes at the study area.  相似文献   

In Situ Ground Water Remediation Using the Trench and Gate System     

Marc W. Bowles  L. R. Bentley  B. Hoyne  D.A. Thomas 《Ground water》2000,38(2):172-181

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A SYNOPTIC CLIMATOLOGY OF COOL-SEASON DERECHO EVENTS     

Mace L. Bentley  Thomas L. Mote 《自然地理学》2013,34(1):21-37

Synoptic-scale environments favorable for producing derechos in the cool season (September through February) are examined with the goal of providing useful techniques for identifying commonalities within derecho activity corridors. Fourteen derechos were identified from two activity corridors located in the southeastern United States and Atlantic seaboard regions between 1986 and 1995. The synoptic environment at the initiation and midpoint of each derecho was then evaluated using surface, upper-air, and the NCAR/NCEP reanalysis data sets. Models are provided in order to illustrate the synoptic-scale environment and to assist meteorologists in recognizing conditions favorable for cool-season derecho formation. Marginal instability and strong synoptic-scale forcing characterized the environments of events in both corridors. The overall synoptic patterns associated with cool-season derecho-producing mesoscale convective systems (DMCSs) resembled environments found with cool-season tornado episodes. Recognition of key elements in this environment could lead to improvements in cool-season severe weather prediction. [Key words: derecho, windstorm, mesoscale convective system (MCS), synoptic climatology, southeast United States.]  相似文献   

Studying Sun–Planet Connections Using the Heliophysics Integrated Observatory (HELIO)     

D. Pérez-Suárez  S. A. Maloney  P. A. Higgins  D. S. Bloomfield  P. T. Gallagher  G. Pierantoni  X. Bonnin  B. Cecconi  V. Alberti  K. Bocchialini  M. Dierckxsens  A. Opitz  A. Le Blanc  J. Aboudarham  R. B. Bentley  J. Brooke  B. Coghlan  A. Csillaghy  C. Jacquey  B. Lavraud  M. Messerotti 《Solar physics》2012,280(2):603-621

The Heliophysics Integrated Observatory (HELIO) is a software infrastructure involving a collection of web services, heliospheric data sources (e.g., solar, planetary, etc.), and event catalogues – all of which are accessible through a unified front end. In this paper we use the HELIO infrastructure to perform three case studies based on solar events that propagate through the heliosphere. These include a coronal mass ejection that intersects both Earth and Mars, a solar energetic particle event that crosses the orbit of Earth, and a high-speed solar wind stream, produced by a coronal hole, that is observed in situ at Earth (L1). A ballistic propagation model is run as one of the HELIO services and used to model these events, predicting if they will interact with a spacecraft or planet and determining the associated time of arrival. The HELIO infrastructure streamlines the method used to perform these kinds of case study by centralising the process of searching for and visualising data, indicating interesting features on the solar disk, and finally connecting remotely observed solar features with those detected by in situ solar wind and energetic particle instruments. HELIO represents an important leap forward in European heliophysics infrastructure by bridging the boundaries of traditional scientific domains.  相似文献   

Aquifer Coefficients Determined from Multiple Well Effects, Fernandina Beach, Florida     

Craig B. Bentley 《Ground water》1979,17(6):525-531

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The stratigraphy of the Inferior Oolite at South Main Road Quarry, Dundry, Avon     

R.B. Chandler  J.H. Callomon  K. Jeffreys  A. Bentley 《Proceedings of the Geologists' Association. Geologists' Association》2006,117(4):345-375

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