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81.
We consider to what extent the long-term dynamics of cyclic solar activity in the form of Grand Minima can be associated with
random fluctuations of the parameters governing the solar dynamo. We consider fluctuations of the alpha coefficient in the
conventional Parker migratory dynamo, and also in slightly more sophisticated dynamo models, and demonstrate that they can
mimic the gross features of the phenomenon of the occurrence of Grand Minima over suitable parameter ranges. The temporal
distribution of these Grand Minima appears chaotic, with a more or less exponential waiting time distribution, typical of
Poisson processes. In contrast, however, the available reconstruction of Grand Minima statistics based on cosmogenic isotope
data demonstrates substantial deviations from this exponential law. We were unable to reproduce the non-Poissonic tail of
the waiting time distribution either in the framework of a simple alpha-quenched Parker model or in its straightforward generalization,
nor in simple models with feedback on the differential rotation. We suggest that the disagreement may only be apparent and
is plausibly related to the limited observational data, and that the observations and results of numerical modeling can be
consistent and represent physically similar dynamo regimes. 相似文献
82.
Richard H. Moss 《Climatic change》2011,108(4):641-658
It is usually necessary to apply incomplete and uncertain information to inform policy and decision making, creating the need
to characterize the state of knowledge and identify when more certain information may be available. After all, some information
is better than none and conversely, even perfect information is of no use if it is available only after a decision has been
made. In scientific assessments for global change, the challenges are particularly acute because of scientific complexity,
long time horizons, and large political and economic stakes, among other factors. Moss and Schneider prepared uncertainty
guidelines for the Third Assessment Report (TAR) of the Intergovernmental Panel on Climate Change (IPCC) that recommended
a process to make expert judgments of levels of confidence and uncertainty more systematic and transparent. The guidance provided
calibrated uncertainty terms to improve communication of findings to users and urged preparation of a traceable account of
the authors’ assessment of the evidence for each major finding. This article reviews the recommendations and their effectiveness
and highlights ensuing critiques and the evolution of uncertainty guidance for subsequent assessment reports. It discusses
emerging challenges in providing science for decision making in the era of increasing model resolution and complexity and
burgeoning interest in information to inform adaptation and mitigation at regional and finer scales. 相似文献
83.
The explosive eruption of kimberlite magma is capable of producing a variety of pyroclast sizes, shapes, and textures. However,
all pyroclastic deposits of kimberlite comprise two main types of pyroclasts: (1) pyroclasts of kimberlite with or without
enclosed olivine crystals and (2) olivine crystals which lack coatings of kimberlite. Here, we propose two hypotheses for
how kimberlite magmas are modified due to explosive eruption: (1) olivine crystals break during kimberlite eruption, and (2)
kimberlite melt can be efficiently separated from crystals during eruption. These ideas are tested against data collected
from field study and image analysis of coherent kimberlite and fragmental kimberlite from kimberlite pipes at Diavik, NT.
Olivines are expected to break because of rapid pressure changes during the explosive eruption. Disruption of kimberlite magma,
and pyroclast production, is driven by ductile deformation processes, rather than by brittle fragmentation. The extent to
which melt separates from olivine crystals to produce kimberlite-free crystals is a direct consequence of the relative proportions
of gas, melt and crystals. Lastly, the properties of juvenile pyroclasts in deposits of pyroclastic kimberlite are used to
index the relative intensity of kimberlite eruptions. A fragmentation index is proposed for kimberlite eruption based on:
(a) crystal size distributions of olivine and on (b) ratios of selvage-free olivine pyroclasts to pyroclasts of kimberlite
with or without olivine crystals. 相似文献
84.
85.
M. M. Katsova L. L. Kitchatinov D. Moss K. Oláh D. D. Sokoloff 《Astronomy Reports》2018,62(8):513-519
The Kepler mission has identified huge flares on various stars, including some solar-type stars. These events are substantially more energetic than solar flares, and are referred to as superflares. Even a low probability of such a superflare occurring on the Sun would be a menace to modern society. A flare comparable in energy to that of superflares was observed on September 24 and 25, 1989 on the binary HK Lac. Unlike the Kepler stars, observations of differential rotation are available for HK Lac. This differential rotation appears to be anti-solar. In the case of anti-solar differential rotation, dynamo models can producemagnetic-activity waves with dipolare symmetry, as well as quasi-stationary magnetic configurations with quadrupolar symmetry. The magnetic energy of such stationary configurations is usually about two orders of magnitude higher than the energy associated with activity waves. We believe that this mechanism could provide sufficient energy to produce superflares on late-type stars. Some simple models in support of this idea are presented. 相似文献
86.
Ian Kraucunas Leon Clarke James Dirks John Hathaway Mohamad Hejazi Kathy Hibbard Maoyi Huang Chunlian Jin Michael Kintner-Meyer Kerstin Kleese van Dam Ruby Leung Hong-Yi Li Richard Moss Marty Peterson Jennie Rice Michael Scott Allison Thomson Nathalie Voisin Tristram West 《Climatic change》2015,129(3-4):573-588
87.
88.
An Cliquet Fabienne Kervarec Dirk Bogaert Frank Maes Betty Queffelec 《Ocean & Coastal Management》2010,53(12):760-768
Public participation is one of the central principles of Integrated Coastal Zone Management (ICZM). However, within current public participation practice in coastal decision making there remain questions regarding whether or not the project leaders or participation processes can be considered legitimate. The paper explores the issue of legitimacy, examining case studies of coastal decision making processes from Belgium and France, focusing on the legal constraints for public participation including degree of formality and government style. It reveals that there are legitimacy issues in public participation related to the legal and institutional framework of the project, as well as to the knowledge base, and characteristics of the stakeholders and their interests. This study concludes that legitimacy issues in an ICZM process cannot be solved entirely through an institutional framework and associated legislation. 相似文献
89.
Publisher's announcement 相似文献
90.
Factors affecting the development of the embryos and production of larvae of the spiny lobster Sagmariasus verreauxi were investigated. Mature lobsters were collected from the fishery in New Zealand and held in captivity until they moulted, mated, and extruded eggs. For females, moulting took place in winter (July/August) and mating occurred 58–88 days later in early spring. The ovigerous females were then held at three temperatures and embryo development monitored at approximately weekly intervals. Mean times to hatch were 55, 75, and 130 days at 20°C, 17°C, and 13°C respectively. The total number of larvae that hatched from each female ranged from 0.97 to 1.4 million. The theoretical temperature at which embryo development ceases (a biological zero) for S. verreauxi, of 9.4°C, was calculated from data on the appearance of the median eye, the eyes and the chromatophores, and the time to hatch. An eye index formula was also derived to allow prediction of time to hatch at a range of temperatures using the cumulative difference between the rearing temperature and the biological zero. First instar phyllosomas from embryos reared at 20°C were significantly smaller than those from 17°C and 13°C but there was no significant difference in fitness. This study shows that hatching can be spread over a number of months, without significantly affecting larval quality, simply by manipulating holding temperature. 相似文献