Lunar surface electric potential changes associated with traversals through the Earth's foreshock     

Michael R. Collier  H. Kent Hills  Timothy J. Stubbs  Jasper S. Halekas  Gregory T. Delory  Jared Espley  William M. Farrell  John W. Freeman  Richard Vondrak 《Planetary and Space Science》2011,59(14):1727-1743

We report an analysis of one year of Suprathermal Ion Detector Experiment (SIDE) Total Ion Detector (TID) “resonance” events observed between January 1972 and January 1973. The study includes only those events during which upstream solar wind conditions were readily available. The analysis shows that these events are associated with lunar traversals through the dawn flank of the terrestrial magnetospheric bow shock. We propose that the events result from an increase in lunar surface electric potential effected by secondary electron emission due to primary electrons in the Earth's foreshock region (although primary ions may play a role as well). This work establishes (1) the lunar surface potential changes as the Moon moves through the terrestrial bow shock, (2) the lunar surface achieves potentials in the upstream foreshock region that differ from those in the downstream magnetosheath region, (3) these differences can be explained by the presence of energetic electron beams in the upstream foreshock region and (4) if this explanation is correct, the location of the Moon with respect to the terrestrial bow shock influences lunar surface potential.  相似文献   

Glacitectonic sedimentary and hydraulic processes at an oscillating ice margin     

Jasper Knight 《Proceedings of the Geologists' Association. Geologists' Association》2012,123(5):714-727

An assemblage of subglacial, ice-terminal and proglacial landforms and sediments provides evidence for the relationship between ice-marginal glacitectonics, sedimentary processes and subglacial and proglacial hydraulic processes at a retreating late Devensian ice margin in north-central Ireland. Deltas were deposited in glacial lakes impounded between the retreating ice margin and the southern Sperrin Mountains, followed by outwash and end moraine formation as the ice margin retreated south. Sediments within the moraines show evidence for ice margin oscillation from two opposing ice margins, including subglacial bedrock rafts and breccias which are separated by glacitectonic shears with silty partings. In adjacent outwash, vertically-disturbed proglacial sands, gravels and silts located in front of moraine positions attest to high hydraulic pressure and subsurface water flow during ice oscillation. The relationship between sedimentary and hydraulic processes in the ice margin region is described by a depositional model which links glacitectonic thrusting and subsurface water flow during ice oscillation to formation of subglacial, ice-terminal and proglacial sediments. The evidence presented in this paper shows that subglacial and proglacial morphosedimentary processes and patterns of sediment deposition are mediated by the presence of proglacial permafrost, which helps direct processes and patterns of groundwater flow.  相似文献   

Radio and millimeter continuum surveys and their astrophysical implications     

Gianfranco De Zotti  Marcella Massardi  Mattia Negrello  Jasper Wall 《Astronomy and Astrophysics Review》2010,18(1-2):1-65

We review the statistical properties of the main populations of radio sources, as emerging from radio and millimeter sky surveys. Recent determinations of local luminosity functions are presented and compared with earlier estimates still in widespread use. A number of unresolved issues are discussed. These include: the (possibly luminosity-dependent) decline of source space densities at high redshifts; the possible dichotomies between evolutionary properties of low- versus high-luminosity and of flat- versus steep-spectrum AGN-powered radio sources; and the nature of sources accounting for the upturn of source counts at sub-milli-Jansky (mJy) levels. It is shown that straightforward extrapolations of evolutionary models, accounting for both the far-IR counts and redshift distributions of star-forming galaxies, match the radio source counts at flux-density levels of tens of μJy remarkably well. We consider the statistical properties of rare but physically very interesting classes of sources, such as GHz Peak Spectrum and ADAF/ADIOS sources, and radio afterglows of γ-ray bursts. We also discuss the exploitation of large-area radio surveys to investigate large-scale structure through studies of clustering and the Integrated Sachs–Wolfe effect. Finally, we briefly describe the potential of the new and forthcoming generations of radio telescopes. A compendium of source counts at different frequencies is given in Supplementary Material.  相似文献   

Detailed seismic stratigraphy of Lago Puyehue: implications for the mode and timing of glacier retreat in the Chilean Lake District     

Katrien Heirman  Marc De Batist  Francois Charlet  Jasper Moernaut  Emmanuel Chapron  Robert Brümmer  Mario Pino  Roberto Urrutia 《第四纪科学杂志》2011,26(7):665-674

Lago Puyehue is a glacigenic lake in the Chilean Lake District (40°S) with a complex deglaciation history. A detailed seismic–stratigraphic study of its sedimentary infill indicates a much earlier retreat of the glacier from the Lago Puyehue basin than the neighbouring glacier from the Lago Rupanco basin. Because of their close proximity, Rupanco meltwater streams played an important part in the depositional processes of Lago Puyehue. A timing discrepancy between the in‐lake ages of a sediment core and the outer‐lake ages of moraine deposits (re)opens the discussion on the timing of deglaciation in the Southern Hemisphere. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Jonkershoek: Africa's oldest catchment experiment - 80 years and counting     

Jasper A. Slingsby  Abri de Buys  Adrian D. A. Simmers  Eric Prinsloo  Greg G. Forsyth  Julia Glenday  Nicky Allsopp 《水文研究》2021,35(4):e14101

The Jonkershoek Forestry Research Station was established in the Mediterranean climate region of South Africa in 1935 to implement a multiple catchment experiment to determine the effects of afforestation on water yield. The experiment consists of six neighbouring catchments previously supporting indigenous fynbos shrublands, five of which were sequentially afforested with Pinus radiata plantations every 8 years from 1940 to 1980 and one kept as the control. They conclusively demonstrated a significant impact of afforestation on streamflow. The treatment catchments have seen subsequent plantation rotations since 1980 and rainfall and streamflow observations have been continued to date. Here we describe the site, experimental design, rainfall and streamflow records, instrumentation, and how to access the data. We also provide details of recently installed instrumentation, including full weather stations, fog gauges, and an eddy covariance flux tower. The Jonkershoek catchment experiment was the core of a globally significant interdisciplinary research programme (1935–1992) that shaped most environmental policies and practices relating to biodiversity, forestry, fire and water in South Africa and beyond. The South African Environmental Observation Network (SAEON) inherited the experiment in 2010 and is maintaining it as a long-term eco-hydrological research platform and global change observatory.  相似文献   

Modelling the effects of land use and climate changes on hydrology in the Ursern Valley,Switzerland          下载免费PDF全文

A. Alaoui  E. Willimann  K. Jasper  G. Felder  F. Herger  J. Magnusson  R. Weingartner 《水文研究》2014,28(10):3602-3614

While many studies have been conducted in mountainous catchments to examine the impact of climate change on hydrology, the interactions between climate changes and land use components have largely unknown impacts on hydrology in alpine regions. They need to be given special attention in order to devise possible strategies concerning general development in these regions. Thus, the main aim was to examine the impact of land use (i.e. bushland expansion) and climate changes (i.e. increase of temperature) on hydrology by model simulations. For this purpose, the physically based WaSiM‐ETH model was applied to the catchment of Ursern Valley in the central Alps (191 km²) over the period of 1983?2005. Modelling results showed that the reduction of the mean monthly discharge during the summer period is due primarily to the retreat of snow discharge in time and secondarily to the reduction in the glacier surface area together with its retreat in time, rather than the increase in the evapotranspiration due to the expansion of the “green alder” on the expense of grassland. The significant decrease in summer discharge during July, August and September shows a change in the regime from b‐glacio‐nival to nivo‐glacial. These changes are confirmed by the modeling results that attest to a temporal shift in snowmelt and glacier discharge towards earlier in the year: March, April and May for snowmelt and May and June for glacier discharge. It is expected that the yearly total discharge due to the land use changes will be reduced by 0.6% in the near future, whereas, it will be reduced by about 5% if climate change is also taken into account. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Characterization of accumulated precipitates during subsurface iron removal     

Doris van Halem  Weren de Vet  Jasper VerberkGary Amy  Hans van Dijk 《Applied Geochemistry》2011,26(1):116-124

The principle of subsurface iron removal for drinking water supply is that aerated water is periodically injected into the aquifer through a tube well. On its way into the aquifer, the injected O₂-rich water oxidizes adsorbed Fe²⁺, creating a subsurface oxidation zone. When groundwater abstraction is resumed, the soluble Fe²⁺ is adsorbed and water with reduced Fe concentrations is abstracted for multiple volumes of the injection water. In this article, Fe accumulation deposits in the aquifer near subsurface treatment wells were identified and characterized to assess the sustainability of subsurface iron removal regarding clogging of the aquifer and the potential co-accumulation of other groundwater constituents, such as As. Chemical extraction of soil samples, with Acid-Oxalate and HNO₃, showed that Fe had accumulated at specific depths near subsurface iron removal wells after 12 years of operation. Whether it was due to preferred flow paths or geochemical mineralogy conditions; subsurface iron removal clearly favoured certain soil layers. The total Fe content increased between 11.5 and 390.8 mmol/kg ds in the affected soil layers, and the accumulated Fe was found to be 56-100% crystalline. These results suggest that precipitated amorphous Fe hydroxides have transformed to Fe hydroxides of higher crystallinity. These crystalline, compact Fe hydroxides have not noticeably clogged the investigated well and/or aquifer between 1996 and 2008. The subsurface iron removal wells even need less frequent rehabilitation, as drawdown increases more slowly than in normal production wells. Other groundwater constituents, such as Mn, As and Sr were found to co-accumulate with Fe. Acid extraction and ESEM-EDX showed that Ca occurred together with Fe and by X-ray Powder Diffraction it was identified as calcite.  相似文献   

The potential of multitemporal Aqua and Terra MODIS apparent thermal inertia as a soil moisture indicator     

Jasper Van doninck  Jan Peters  Bernard De Baets  Eva M. De Clercq  Els Ducheyne  Niko E.C. Verhoest 《International Journal of Applied Earth Observation and Geoinformation》2011

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Maladaptive trajectories of change in Makira, Solomon Islands   总被引：2，自引：0，他引：2  

Ioan Fazey  Nathalie Pettorelli  Jasper Kenter  Daniel Wagatora  Daniel Schuett 《Global Environmental Change》2011,21(4):1275-1289

Trajectories of change are dynamic processes of individual, group and/or societal responses to change which create further change and responses, with outcomes that reflect the cumulative properties of those processes. Understanding trajectories of change is an important initial step for designing appropriate adaptation strategies because even though responses may enable people to cope with change in the short term, the accumulated responses of individuals can generate undesirable maladaptive outcomes over longer periods of time. This paper examines trajectories of change in Kahua, Solomon Islands, where people have traditionally relied on subsistence activities and have in the past been subsistence affluent. Participatory methods, including 76 focus group discussions in 38 communities with 821 individuals, were used to determine changes in the region and its drivers. A conceptual model was developed of the underlying feedback processes within the Kahua social–ecological system. The results show that communities are facing rapid and extensive changes. Most changes, however, are being driven by the two key drivers of population growth and a strong desire for monetary prosperity that act synergistically to generate stress in communities. People are generally responding by focusing on income generation, which is reinforcing stress in communities and resulting in maladaptive trajectories of change. The results suggest development policy in the Solomon Islands needs to: (1) take the challenges of population growth much more seriously; (2) place greater effort on development activities that reduce per capita impact on the environment; (3) improve management of the high expectations for monetary prosperity; (4) increase emphasis on wellbeing aspects of development rather than income generation per se, and (5) better align development with existing adaptation strategies to ensure that vulnerability to future global change does not increase.  相似文献   

The importance of deliberation in valuing ecosystem services in developing countries—Evidence from the Solomon Islands     

Jasper O. Kenter  Tony Hyde 《Global Environmental Change》2011,21(2):505-521

Monetary valuation of ecosystem services enables more accurate accounting of the environmental costs and benefits of policies, but this has rarely been applied in developing countries. In such contexts, there are particular methodological and epistemological challenges that require novel valuation methodologies. This paper introduces a new participatory, deliberative choice experiment approach conducted in the Solomon Islands. The research aimed to determine the value people placed on ecosystem services and whether participatory interventions to elicit deeper held values influenced the preferences expressed. Results found that the initial willingness to pay for a number of tropical forest ecosystem services amounted to 30% of household income. Following deliberative intervention exercises, key ecosystem services effectively became priceless as participants were unwilling to trade them off in the choice experiment scenarios, regardless of financial cost. The group based deliberative approach, combined with participatory interventions, also resulted in significant learning for participants. This included a more sophisticated view of ecological-cultural linkages, greater recognition of deeper held values, and greater awareness of the consequences of human actions for the environment. The use of a group-based participatory approach instead of a conventional individual survey helped to overcome many of the practical difficulties associated with valuation in developing countries. Given the impact of learning on valuation outcomes, participation and deliberation should be integrated into valuation of any complex good, both in developing and developed economies. However, such a methodology raises questions about how valuation can deal with unwillingness to trade-off key ecosystem services, which results in the breakdown of monetary valuation methods. Evaluation of the appropriateness of valuation processes and methodologies for assessing deeper held values and use of mixed-method approaches will be essential to ensure policies take into account the extent to which human life is dependent on ecosystem services.  相似文献