Radiation transfer of gyrosynchrotron emission in stellar environments     

Michelle C. Storey 《Solar physics》1996,168(2):435-447

Non-thermal radio emission has been detected from several kinds of active stars. Polarization and intensity measurements of the quiescent (i.e. non-flaring) emission indicate gyrosynchrotron emission. A three-dimensional magnetic field model for the stellar field is presented and the gyrosynchrotron intensity and polarization emerging from such a model is calculated and compared with observations. Model spectra agree well with observations. Model polarization results indicate that the emission region is more complex than the simple model and may indicate the presence of multipole components in the field, small loops of flux near the stellar surface and significant energy loss in the radiating electron distribution over time.  相似文献   

Eolian controlled modification of the martian south polar layered deposits     

Michelle R. Koutnik  Shane Byrne  Anthony D. Toigo 《Icarus》2005,174(2):490-501

Data from the Mars Orbiter Laser Altimeter (MOLA) and Mars Orbiter Camera (MOC) aboard the Mars Global Surveyor (MGS) mission and the Thermal Emission Imaging System (THEMIS) aboard the Mars Odyssey mission have revealed unique surface features in a particular region of the South Polar Layered Deposits (SPLD). The dominant morphology is large-scale quasi-parallel grooves that extend for hundreds of kilometers with only tens of meters of vertical relief, that we have termed here the “Wire Brush” terrain. The grooves are also transected by disjointed, yet roughly continuous, low-relief sinuous ridges that cross roughly perpendicular to the trend-direction of the large-scale grooves and show only tens of meters of relief. We interpret these ridges to be eroded remnants of folded layers. At the northern end of the large-scale grooves there are non-symmetric mounds. They are frequently preceded by a significant depression and/or trailing grooves that are parallel to the Wire Brush trend. We find that a two-stage process involving winds that intermittently remove a low-density crust exposing the underlying ice to ablation is the interpretation that best explains the multitude of features observed here. These features appear to be currently inactive indicating higher winds in previous epochs.  相似文献   

Erratum to: The Quadrennial Ozone Symposium 2016     

Sophie GODIN-BEEKMANN  Irina PETROPAVLOSKIKH  Stefan REIS  Paul NEWMAN  Wolfgang STEINBRECHT  Markus REX  Michelle L. SANTEE  Richard S. ECKMAN  Xiangdong ZHENG  Matthew B. TULLY  David S. STEVENSON  Paul YOUNG  John PYLE  Mark WEBER  Johanna TAMMINEN  Gina MILLS  Alkiviadis F. BAIS  Clare HEAVISIDE  Christos ZEREFOS 《大气科学进展》2018,35(3):368-369

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Transport of elemental mercury in the unsaturated zone from a waste disposal site in an arid region     

Michelle A. Walvoord  Brian J. Andraski  David P. Krabbenhoft  Robert G. Striegl 《Applied Geochemistry》2008

Mercury contained in buried landfill waste may be released via upward emission to the atmosphere or downward leaching to groundwater. Data from the US Geological Survey’s Amargosa Desert Research Site (ADRS) in arid southwestern Nevada reveal another potential pathway of Hg release: long-distance (10² m) lateral migration of elemental Hg (Hg⁰) through the unsaturated zone. Gas collected from multiple depths from two instrumented boreholes that sample the entire 110-m unsaturated zone thickness and are located 100 and 160 m away from the closest waste burial trench exhibit gaseous Hg concentrations of up to 33 and 11 ng m⁻³, respectively. The vertical distribution of gaseous Hg in the borehole closest to the disposal site shows distinct subsurface peaks in concentration at depths of 1.5 and 24 m that cannot be explained by radial diffusive transport through a heterogeneous layered unsaturated zone. The inability of current models to explain gaseous Hg distribution at the ADRS highlights the need to advance the understanding of gas-phase contaminant transport in unsaturated zones to attain a comprehensive model of landfill Hg release.  相似文献   

Splintered networks: The colonial and contemporary waters of Jakarta     

Michelle Kooy  Karen Bakker 《Geoforum》2008,39(6):1843-1858

This paper queries the relevance of the ‘splintering urbanism’ thesis to postcolonial cities of the South, and responds to calls for the production of a decentered theory of urbanization through a case study of Jakarta. Drawing on archival and interview data, the paper demonstrates that Jakarta has, since its inception, been characterized by a high degree of differentiation of access to water supply, and of fragmentation of water supply networks. We document the origins of this fragmentation in the colonial era, and trace the legacy of the colonial constructions within the postcolonial city. Moreover, we demonstrate that the introduction of private sector management (in 1988) has not significantly disrupted, and certainly not caused, this pattern. In short, we provide evidence to support our claim that Jakarta’s water supply system is ‘splintered’ rather than ‘splintering’, and demonstrate that this phenomenon was not caused by the rise (or fall) of the ‘modern infrastructural ideal’. In order to explain this sustained fragmentation of infrastructure and access, the paper develops a conceptual framework of postcolonial governmentality that emphasizes the interrelationship between materiality, governmentality, identity, and urbanization, in particular through demonstrating how contested and evolving process of social differentiation are linked to the differentiation of water supply infrastructures and of urban spaces. Although we are wary of any simplistic comparisons between the colonial past and present, we argue that the optic of postcolonial governmentality provides a powerful lens for dissecting the power relations that continue to structure access to water supply and urban space in cities in the South.  相似文献   

Mapping Zones of Contaminated Ground-Water Discharge Using Creek-Bottom-Sediment Vapor Samplers, Aberdeen Proving Ground, Maryland   总被引：1，自引：0，他引：1  

Don A. Vroblesky  Michelle M. Lorah  Stephen P. Trimble 《Ground water》1991,29(1):7-12

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Prospecting for Zones of Contaminated Ground-Water Discharge to Streams Using Btottom-Sediment Gas Bubbles     

Don A. Vroblesky  Michelle M. Lorah 《Ground water》1991,29(3):333-340

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Investigations of road sediment in an industrial corridor near low-income housing in Hamilton,Ohio     

Lonnie Flett  Mark P. S. Krekeler  Michelle Burke 《Environmental Earth Sciences》2016,75(16):1156

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High Resolution Deterministic Prediction System (HRDPS) Simulations of Manitoba Lake Breezes     

Scott Kehler  John Hanesiak  Michelle Curry  David Sills  Neil Taylor 《大气与海洋》2016,54(2):93-107

The Effects of Lake Breezes On Weather–Manitoba (ELBOW-MB) field project, conducted around Lakes Manitoba and Winnipeg in July 2013, was the first in-depth field study of lake breezes in Manitoba, Canada. Using observational data collected during ELBOW-MB and output from the 2.5?km Canadian High Resolution Deterministic Prediction System (HRDPS), comparisons were made between HRDPS output and observational data to determine whether the HRDPS can simulate Manitoba lake breezes. The model comparisons considered various lake-breeze characteristics, such as depth, inland penetration distance, and initiation and dissipation time. In addition, cross-sections of lake-breeze circulations were analyzed. The results show that the HRDPS was able to correctly simulate lake breezes, or lack thereof, in 78% of cases on Lake Winnipeg and 68% of cases on Lake Manitoba. Modelled lake-breeze initiation and dissipation times were found to be too early in some cases and too late in others when compared with observations. Overall, it was found that the HRDPS was able to simulate most aspects of lake breezes, although inland penetration distance was one characteristic that the HRDPS was not able to simulate realistically.  相似文献   

Water availability and land subsidence in the Central Valley,California, USA     

Claudia C. Faunt  Michelle Sneed  Jon Traum  Justin T. Brandt 《Hydrogeology Journal》2016,24(3):675-684

The Central Valley in California (USA) covers about 52,000 km² and is one of the most productive agricultural regions in the world. This agriculture relies heavily on surface-water diversions and groundwater pumpage to meet irrigation water demand. Because the valley is semi-arid and surface-water availability varies substantially, agriculture relies heavily on local groundwater. In the southern two thirds of the valley, the San Joaquin Valley, historic and recent groundwater pumpage has caused significant and extensive drawdowns, aquifer-system compaction and subsidence. During recent drought periods (2007–2009 and 2012-present), groundwater pumping has increased owing to a combination of decreased surface-water availability and land-use changes. Declining groundwater levels, approaching or surpassing historical low levels, have caused accelerated and renewed compaction and subsidence that likely is mostly permanent. The subsidence has caused operational, maintenance, and construction-design problems for water-delivery and flood-control canals in the San Joaquin Valley. Planning for the effects of continued subsidence in the area is important for water agencies. As land use, managed aquifer recharge, and surface-water availability continue to vary, long-term groundwater-level and subsidence monitoring and modelling are critical to understanding the dynamics of historical and continued groundwater use resulting in additional water-level and groundwater storage declines, and associated subsidence. Modeling tools such as the Central Valley Hydrologic Model, can be used in the evaluation of management strategies to mitigate adverse impacts due to subsidence while also optimizing water availability. This knowledge will be critical for successful implementation of recent legislation aimed toward sustainable groundwater use.  相似文献