On the prevalence of radio-loud active galactic nuclei in brightest cluster galaxies: implications for AGN heating of cooling flows     

P. N. Best  A. von der Linden  G. Kauffmann  T. M. Heckman  C. R. Kaiser 《Monthly notices of the Royal Astronomical Society》2007,379(3):894-908

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Bastille Day Event: A Radio Perspective     

Reiner  M.J.  Kaiser  M.L.  Karlický  M.  Jiřička  K.  Bougeret  J.-L. 《Solar physics》2001,204(1-2):121-137

We describe the radio signatures that led up to and concluded the solar eruptive event of 14 July 2000 (Bastille Day Event). These radio signatures provide a means of remotely sensing the associated solar activity and transient phenomena. For many days prior to the Bastille Day Event kilometric Type III radio storm emissions were observed that were presumably associated with the active region NOAA 9077. These storm emissions continued until the X5.7 flare at ∼ 10 UT on 14 July 2000 that characterized the Bastille Day Event, then ceased abruptly. The Bastille Day Event itself produced very intense, complex, long-duration Type III-like radio emissions, which appear to have been associated with electrons generated (accelerated) deep in the solar corona. The coronal mass ejection (CME) associated with the Bastille Day Event generated decametric to kilometric Type II radio emissions as the CME propagated through the solar corona and interplanetary medium. The frequency drift of these Type II radio emissions are related to the dynamics of the propagating CME and indicate that the CME experienced significant deceleration as it propagated from the high corona into the interplanetary medium.  相似文献   

Radio galaxies with a 'double-double morphology'– I. Analysis of the radio properties and evidence for interrupted activity in active galactic nuclei     

Arno P. Schoenmakers  †  A. G. de Bruyn  H. J. A. Röttgering  H. van der Laan  C. R. Kaiser 《Monthly notices of the Royal Astronomical Society》2000,315(2):371-380

We present four Mpc-sized radio galaxies which consist of a pair of double-lobed radio sources, aligned along the same axis, and with a coinciding radio core. We call these peculiar radio sources 'double-double' radio galaxies (DDRGs) and propose a general definition of such sources: a 'double-double' radio galaxy consists of a pair of double radio sources with a common centre. Furthermore, the two lobes of the inner radio source must have a clearly extended, edge-brightened radio morphology. Adopting this definition, we find several other candidate DDRGs in the literature. We find that in all sources the smaller (inner) pair of radio lobes is less luminous than the larger (outer) pair, and that the ratio of 1.4-GHz flux density of these two pairs appears to be anticorrelated with the projected linear size of the inner source. Also, the outer radio structures are large, exceeding 700 kpc. We discuss possible formation scenarios of the DDRGs, and we conclude that an interruption of the jet-forming central activity is the most likely mechanism. For one of our sources (B 1834+620) we have been able observationally to constrain the length of time of the interruption to a few Myr. We discuss several scenarios for the cause of the interruption, and suggest multiple encounters between interacting galaxies as a possibility. Finally, we discuss whether such interruptions help the formation of extremely large radio sources.  相似文献   

A Review of Louisiana Drilling and Production Activity, 1980–2011     

Mark J. Kaiser 《Natural Resources Research》2014,23(1):99-140

Louisiana plays an important role in domestic oil and natural gas production, and in 2012 ranked sixth in oil production and third in gas production in the United States. Conventional oil and gas production in Louisiana has been declining steadily over the past four decades, while unconventional gas production has seen spectacular growth in recent years, effectively doubling the state’s natural gas output over three years. The structural changes impacting Louisiana’s oil and gas industry are complex and dynamic, and to better understand the relationships between activity drivers, a review of drilling and production data between 1980 and 2011 is performed and correlative relationships are developed. Drilling and completion trends, including completion and success rate statistics and drilled footage, are summarized by region. Correlative relationships are established between measured footage and the number of wells drilled, drilling activity, abandonments, and commodity price. We show that drilling activity in North Louisiana is highly responsive to changing oil prices, whereas in South Louisiana, activity is relatively inelastic. Well abandonments are shown to be negatively related to commodity prices. Horizontal, directional, active, idle, and orphaned well inventories are summarized.  相似文献   

Hot and cold bubbles in M87     

Christian R. Kaiser 《Monthly notices of the Royal Astronomical Society》2003,343(4):1319-1326

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Haynesville Louisiana Drilling and Production Update 2012     

Mark J. Kaiser 《Natural Resources Research》2015,24(1):33-51

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Impact of the 2004 Indian Ocean tsunami along the Tamil Nadu coastline: field survey review and numerical simulations     

G. Gopinath  F. Løvholt  G. Kaiser  C. B. Harbitz  K. Srinivasa Raju  M. Ramalingam  Bhoop Singh 《Natural Hazards》2014,72(2):743-769

The 2004 Indian Ocean tsunami had a significant impact on the Tamil Nadu coast in India. In this paper, a range of field survey data collected by different survey teams available in literature have been analyzed and compiled to serve as a basis for validation of numerical tsunami simulations. The individual field surveys reveal a significant scatter in the run-up data between the different teams, which point out that the uncertainty in these data must be taken into account when using them for validation. The inundation of the 2004 Indian Ocean tsunami is simulated for the coastlines of Chennai and Nagapattinam based on high-resolution topography. Different spatially uniform Manning friction as well as heterogeneous friction maps is used. Overall, the simulation results showed a good agreement with the field observations, but there are also some observed spatial variability in the goodness of the fit between the data and simulations. In some areas, clear discrepancies are found. The results obtained using detailed land use maps including spatially variable friction are not significantly more accurate than those employing spatially constant values. For most areas, parameters indicating relatively low friction provided best match with the observations. This may also suggest that the inundation is often strongly governed by local variations in topography.  相似文献   

3D coupled fluid and heat transport simulations of the Northeast German Basin and their sensitivity to the spatial discretization: different sensitivities for different mechanisms of heat transport     

Björn Onno Kaiser  Mauro Cacace  Magdalena Scheck-Wenderoth 《Environmental Earth Sciences》2013,70(8):3643-3659

Based on a numerical model of the Northeast German Basin (NEGB), we investigate the sensitivity of the calculated thermal field as resulting from heat conduction, forced and free convection in response to consecutive horizontal and vertical mesh refinements. Our results suggest that computational findings are more sensitive to consecutive horizontal mesh refinements than to changes in the vertical resolution. In addition, the degree of mesh sensitivity depends strongly on the type of the process being investigated, whether heat conduction, forced convection or free thermal convection represents the active heat driver. In this regard, heat conduction exhibits to be relative robust to imposed changes in the spatial discretization. A systematic mesh sensitivity is observed in areas where forced convection promotes an effective role in shorten the background conductive thermal field. In contrast, free thermal convection is to be regarded as the most sensitive heat transport process as demonstrated by non-systematic changes in the temperature field with respect to imposed changes in the model resolution.  相似文献   

Late Pleistocene and Holocene terrestrial geomorphodynamics and soil formation in northeastern Germany: a review of geochronological data     

Christoph Kappler  Knut Kaiser  Mathias Küster  Alexander Nicolay  Alexander Fülling  Oliver Bens 《自然地理学》2013,34(5):405-432

ABSTRACT

This study is based on 616 geochronological ages from aeolian and colluvial sediments as well as paleosols, representing the largest database of geochronological data from northeastern Germany available to date. Cumulative probability density functions for radiocarbon data and kernel density estimates for luminescence data were created covering the last 15 ka. The data analysis aimed at the identification of changes and their drivers in geomorphodynamics and soil formation. The ages representing aeolian activity cluster in the Late Glacial, the Early Holocene, and the Late Holocene, where the first two clusters are assumed to result mostly from climatic impact with only a minor share of human impact triggering the mobilization of aeolian sediments. The third cluster is considered to result mainly from human impact. The Late Glacial to Early Holocene activity phase is interrupted by a phase of surface stability around 11.5–12.7 ka, which is indicated by the occurrence of initial soil formations of Finow and Usselo types. Colluvial sedimentation predominantly occurred during the last 7 ka and clearly accelerated since the last 1000 a. According to the ages of specific paleosol types, related soil-forming processes started already in the Late Glacial and were completed in the Holocene.  相似文献   

Environmental changes,remote sensing,and infrastructure development: The case of Egypt's East Port Said harbour     

M.F. Kaiser 《Applied geography (Sevenoaks, England)》2009,29(2):280-288

Using Landsat TM data, this article examines the environmental impact of the East Port Said harbour project on the surrounding landscape. The optimum three-band combination and the most appropriate multispectral bands were selected to enhance the images and monitor land cover changes for the periods of 1984–1991 and 1991–2003. The results indicate that wetland areas declined from 103 km² in 1984 to 30 km² in 2003. In addition, the surface area of El-Malha Lake has shrunk from 27 km² to 18 km² over the same period. In contrast, the area covered by salt crust has increased from 11 km² in 1984 to 19 km² in 2003. Urban land use and designed cultivated lands were also significant in 2003, covering 49 km² and 71 km², respectively. The rate of shoreline change between 1984 and 2003, the period when the East Port Said harbour was constructed, was calculated. Vector data indicate that the rate of shoreline loss was ?13 m/year from 1984 to 1991 and ?15 m/year from 1991 to 2003. Despite the fact that construction of the East Port Said harbour caused significant changes in the study area, there are several factors controlling coastline and land cover changes including industrial development and fish cultivation farms.  相似文献