How Does Large Flaring Activity from the Same Active Region Produce Oppositely Directed Magnetic Clouds?     

Louise K. Harra  Nancy U. Crooker  Cristina H. Mandrini  Lidia van Driel-Gesztelyi  Sergio Dasso  Jingxiu Wang  Heather Elliott  Gemma Attrill  Bernard V. Jackson  Mario M. Bisi 《Solar physics》2007,244(1-2):95-114

We describe the interplanetary coronal mass ejections (ICMEs) that occurred as a result of a series of solar flares and eruptions from 4 to 8 November 2004. Two ICMEs/magnetic clouds occurring from these events had opposite magnetic orientations. This was despite the fact that the major flares related to these events occurred within the same active region that maintained the same magnetic configuration. The solar events include a wide array of activities: flares, trans-equatorial coronal loop disappearance and reformation, trans-equatorial filament eruption, and coronal hole interaction. The first major ICME/magnetic cloud was predominantly related to the active region 10696 eruption. The second major ICME/magnetic cloud was found to be consistent with the magnetic orientation of an erupting trans-equatorial filament or else a rotation of 160° of a flux rope in the active region. We discuss these possibilities and emphasize the importance of understanding the magnetic evolution of the solar source region before we can begin to predict geoeffective events with any accuracy.  相似文献   

Two Tales of a City: detecting socio-economic disadvantage in an ‘advantaged’ Australian urban centre     

Xavier Goldie  Isabel Kakuk  Gemma Wood 《The Australian geographer》2014,45(4):521-540

Understanding the distribution of socio-economic status (SES) within and between communities of varying spatial scales is vital for equitable and effective resource delivery and policy development. In Australia, the Socio-economic Indexes for Areas (SEIFA) have been used extensively for these purposes, in both research and government service delivery. As area-based averages, however, their use in these areas is potentially confounded by the ecological fallacy and the modifiable areal unit problem (MAUP), statistical issues which have widespread implications for the use of spatial data. The Socio-economic Index for Individuals (SEIFI) is an individual-based index developed by the ABS to quantify SES at an individual level for 15–64 year-old Australians. Previous work investigated the potential disparities between these area- and individual-level indices, showing that considerable disparities exist, particularly in the Australian Capital Territory (ACT). Using spatial autocorrelation and pair-wise proportion analyses, we show that there was considerable diversity in individual-level SES at a very fine level of geography in 2006, a unique pattern in Australia. We also show that the SES ranking of areas within the ACT is, in many instances, not indicative of the proportions of individuals living within that area experiencing high levels of relative socio-economic disadvantage. We show that between 65–95 per cent of the ACT's disadvantaged population are masked within areas ranked as advantaged, depending on the index and level of spatial aggregation. Our results suggest that the use of SEIFA as a proxy for individual level disadvantage is highly problematic at both a theoretical and practical level, and necessitates further development of an individual- or household-level index as part of the regular suite of socio-economic indices produced by the ABS.  相似文献   

Imaging the recent sediment dynamics of the Galicia Bank region (Atlantic,NW Iberian Peninsula)     

Gemma Ercilla  David Casas  Juan T. Vázquez  Jorge Iglesias  Luís Somoza  Carmen Juan  Teresa Medialdea  Ricardo León  Ferran Estrada  Soledad García-Gil  Marcel.lí Farran  Fernando Bohoyo  Margarita García  Adolfo Maestro  ERGAP Project  Cruise Teams 《Marine Geophysical Researches》2011,32(1-2):99

Multibeam bathymetry, high resolution multi-channel, and very high resolution single-channel (3.5 kHz) seismic records were used to depict the complex geomorphology that defines the Galicia Bank region (Atlantic, NW Iberian Peninsula). This region (≈620–5,000 m water depth) is characterized by a great variety of features: structural features (scarps, highs, valleys, fold bulges), fluid dynamics-related features (structural undulations and collapse craters), mass-movement features (gullies, channels, mass-flow deposits, slope-lobe complexes, and mass-transport deposits), bottom-current features (moats, furrows, abraded surface, sediment waves, and drifts), (hemi)pelagic features, mixed features (abraded surfaces associated to mixed sediments) and bioconstructions. These features represent architectural elements of four sedimentary systems: slope apron, contouritic, current-controlled (hemi)pelagic, and (hemi)pelagic. These systems are a reflection of different sedimentary processes: downslope (mass transport, mass flows, turbidity flows), alongslope (bottom currents of Mediterranean Outflow Water, Labrador Sea Water, North Atlantic Deep Water, and Lower Deep Water), vertical settling, and the interplay between them. The architectural and sediment dynamic complexities, for their part, are conditioned by the morphostructural complexity of the region, whose structures (exposed scarps and highs) favor multiple submarine sediment sources, affect the type and evolution of the mass-movement processes, and interact with different water masses. This region and similar sedimentary environments far from the continental sediment sources, as seamounts, are ideal zones for carrying out submarine source-to-sink studies, and can represent areas subject to hazards, both geologic and oceanographic in origin.  相似文献   

Impact of pulsed Atlantic water inflow into the Alboran Basin at the time of the Zanclean flooding     

Ferran Estrada  Gemma Ercilla  Christian Gorini  Bel��n Alonso  Juan Tom��s V��zquez  Daniel Garc��a-Castellanos  Carmen Juan  Andr��s Maldonado  Abdellah Ammar  Mohammed Elabbassi 《Geo-Marine Letters》2011,31(5-6):361-376

The study of more than 500 single- and multichannel seismic records enabled the generation of a detailed palaeo-bathymetric map of the Messinian surface over most of the Alboran Basin, Western Mediterranean. This regional surface is characterized by several erosional features (channels, terraces and canyons) and topographic highs (structural, volcanic and diapiric in origin). The most prominent feature is the incised Zanclean Channel crossing the entire basin, its entrenchment having been associated with the opening of the Strait of Gibraltar and subsequent inflow of Atlantic waters. The incision depth of the channel is variable, suggesting local variations in the erosive capacity of the Atlantic inflow, conditioned mainly by the regional basin topography and the local presence of topographic highs. Adjacent to this channel along the Spanish and Moroccan margins, and near the Strait of Gibraltar, several submarine terraces developed at different depths suggest a pulsed flooding of the Alboran Basin. There could have been two major inflow phases of Atlantic water, one shortly before and another during the Zanclean flooding, the latter accompanied by periods of relative sea-level stillstands that enabled terrace development. Alternatively, these features were all generated during the main flooding evident and subsequent pulsed infilling of the basin.  相似文献   

Knowledge gaps in our perceptual model of Great Britain's hydrology     

Thorsten Wagener  Simon J. Dadson  David M. Hannah  Gemma Coxon  Keith Beven  John P. Bloomfield  Wouter Buytaert  Hannah Cloke  Paul Bates  Joseph Holden  Louise Parry  Rob Lamb  Nick A. Chappell  Matthew Fry  Gareth Old 《水文研究》2021,35(7):e14288

There is a no lack of significant open questions in the field of hydrology. How will hydrological connectivity between freshwater bodies be altered by future human alterations to the hydrological cycle? Where does water go when it rains? Or what is the future space–time variability of flood and drought events? However, the answers to these questions will vary with location due to the specific and often poorly understood local boundary conditions and system properties that control the functional behaviour of a catchment or any other hydrologic control volume. We suggest that an open, shared and evolving perceptual model of a region's hydrology is critical to tailor our science questions, as it would be for any other study domain from the plot to the continental scale. In this opinion piece, we begin to discuss the elements of and point out some knowledge gaps in the perceptual model of the terrestrial water cycle of Great Britain. We discuss six major knowledge gaps and propose four key ways to reduce them. While the specific knowledge gaps in our perceptual model do not necessarily transfer to other places, we believe that the development of such perceptual models should be at the core of the debate for all hydrologic communities, and we encourage others to have a similar debate for their hydrologic domain.  相似文献   

Long-term fluid circulation in extensional faults in the central Catalan Coastal Ranges: P–T constraints from neoformed chlorite and K-white mica     

Irene Cantarero  Pierre Lanari  Olivier Vidal  Gemma Alías  Anna Travé  Vinyet Baqués 《International Journal of Earth Sciences》2014,103(1):165-188

The neoformation of chlorite and K-white mica in fault rocks from two main faults of the central Catalan Coastal Ranges, the Vallès and the Hospital faults, has allowed us to constrain the P–T conditions during fault evolution using thermodynamic modeling. Crystallization of M1 and M2 muscovite and microcline occured as result of deuteric alteration during the exhumation of the pluton (290 °C > T > 370 °C) in the Permian. After that, three tectonic events have been distinguished. The first tectonic event, attributed to the Mesozoic rifting, is characterized by precipitation of M3 and M4 phengite together with chlorite and calcite C1 at temperatures between 190 and 310 °C. The second tectonic event attributed to the Paleogene compression has only been identified in the Hospital fault with precipitation of low-temperature calcite C2. The shortcut produced during inversion of the Vallès fault was probably the responsible for the lack of neoformed minerals within this fault. Finally, the third tectonic event, which is related to the Neogene extension, is characterized in the Vallès fault by a new generation of chlorite, associated with calcite C4 and laumontite, formed at temperatures between 125 and 190 °C in the absence of K-white mica. Differently, the Hospital fault is characterized by the precipitation of calcite C3 during the syn-rift stage at temperatures around 150 °C and by low-temperature fluids precipitating calcites C5, C6 and PC1 during the post-rift stage. During the two extensional events (Mesozoic and Neogene), faults acted as conduits for hot fluids producing anomalous high geothermal gradients (50 °C/km minimum).  相似文献   

How Reliable are Citizen‐Derived Scientific Data? Assessing the Quality of Contrail Observations Made by the General Public     

Amy Fowler  J. Duncan Whyatt  Gemma Davies  Rebecca Ellis 《Transactions in GIS》2013,17(4):488-506

Citizen science projects encourage the general public to participate in scientific research. Participants can contribute large volumes of data over broad spatial and temporal frames; however, the challenge is to generate data of sufficient quality to be useable in scientific research. Most observations made by citizen‐scientists can be independently verified by “experts”. However, verification is more problematic when the phenomena being recorded are short‐lived. This article uses a GIS methodology to verify the quality of contrail observations made by the general public as part of the OPAL Climate Survey. We verify observations using datasets derived from a variety of different sources (experts, models and amateur enthusiasts) with different spatial and temporal properties which reflect the complex 3D nature of the atmosphere. Our results suggest that ～70% of citizen observations are plausible, based on favorable atmospheric conditions and the presence or absence of aircraft; a finding which is in keeping with other, more conventional citizen science projects. However, questions remain as to why the quality of the citizen‐based observations was so high. Given the lack of supporting data on observers, it is impossible to determine whether the dataset was generated by the activities of many participants or a small but dedicated number of individual observers.  相似文献   

Esterases activities and lipid peroxidation levels in muscle tissue of the shanny Lipophrys pholis along several sites from the Portuguese Coast     

Solé M  Lobera G  Lima D  Reis-Henriques MA  Santos MM 《Marine pollution bulletin》2008,56(5):999-1007

This study is part of a project aiming to validate the use of the intertidal shanny Lipophorys pholis as a sentinel species in pollution monitoring in NW European marine ecosystems. To this end, a characterisation of acethylcholin (AChE), butyrylcholin (BChE) and propionylcholin (PrChE) esterases in L. pholis muscle was performed and the results indicated that AChE was predominant. Furthermore, the use of eserine sulphate and BW284c51 (0.64–800 μM), and iso-OMPA (0.08–16 mM), confirmed the measurement of true cholinesterases (ChEs) as well as the presence of pseudocholinesterases. The field application of these markers to L. pholis, sampled in seven locations along the Portuguese coast, revealed that fish were likely to be affected by neurotoxic compounds. This was indicated by the significant depletion of AChE (p < 0.05) in animals collected at urban and industrialised sites, compared with those from reference locations. The inclusion of a marker of effect, measured as lipid peroxidation levels in muscle tissue, also revealed the existence of site differences. Overall, the study further validates the utility of L. pholis in pollution monitoring studies.  相似文献   

Reintroduced large wood modifies fine sediment transport and storage in a lowland river channel          下载免费PDF全文

Chris Parker  Alexander J. Henshaw  Gemma L. Harvey  Carl D. Sayer 《地球表面变化过程与地形》2017,42(11):1693-1703

This paper explores changes in suspended sediment transport and fine sediment storage at the reach and patch scale associated with the reintroduction of partial large wood (LW) jams in an artificially over‐widened lowland river. The field site incorporates two adjacent reaches: a downstream section where LW jams were reintroduced in 2010 and a reach immediately upstream where no LW was introduced. LW pieces were organized into ‘partial’ jams incorporating several ‘key pieces’ which were later colonized by substantial stands of aquatic and wetland plants. Reach‐scale suspended sediment transport was investigated using arrays of time‐integrated suspended sediment samplers. Patch‐scale suspended sediment transport was explored experimentally using turbidity sensors to track the magnitude and velocity of artificially generated sediment plumes. Fine sediment storage was quantified at both reach and patch scales by repeat surveys of fine sediment depth. The results show that partial LW jams influence fine sediment dynamics at both the patch and reach scale. At the patch‐scale, introduction of LW led to a reduction in the concentration and increase in the time lag of released sediment plumes within the LW, indicating increased diffusion of plumes. This contrasted with higher concentrations and lower time lags in areas adjacent to the LW; indicating more effective advection processes. This led to increased fine sediment storage within the LW compared with areas adjacent to the LW. At the reach‐scale there was a greater increase in fine sediment storage through time within the restored reach relative to the unrestored reach, although the changes in sediment transport responsible for this were not evident from time‐integrated suspended sediment data. The results of the study have been used to develop a conceptual model which may inform restoration design. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Using GIS to Investigate Spatial and Temporal Variations in Upland Rainfall     

Emma JS Ferranti  J Duncan Whyatt  Roger J Timmis  Gemma Davies 《Transactions in GIS》2010,14(3):265-282

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