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681.
682.
P. C. Liewer I. González Hernández J. R. Hall C. Lindsey X. Lin 《Solar physics》2014,289(10):3617-3640
We test the reliability of helioseismic far-side active-region predictions, made using Dopplergrams from both the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO) and the Global Oscillation Network Group (GONG), by comparison with far-side observation of solar activity from the Solar TErrestrial RElations Observatory (STEREO). Both GONG and HMI produce seismic Carrington maps that show strong magnetic-field regions, labeling predictions of far-side active regions that have a probability ≥?70 %. By visual comparison of these prediction maps with STEREO extreme ultraviolet (EUV) Carrington maps, we determine whether or not solar activity, as evidenced as brightness in EUV, is observed at the predicted locations. We analyzed nine months of data from 2011 and 2012. For both GONG and HMI, we find that for approximately 90 % of the active-region predictions, activity/brightness is observed in EUV at the predicted location. We also investigated the success of GONG and HMI at predicting large active regions before they appear at the east limb as viewed from Earth. Of the 27 identified large east-limb active regions in the nine months of data analyzed, GONG predicted 15 (55 %) at least once within the week prior to Earth-side appearance and HMI predicted 13 (48 %). Based on the STEREO far-side EUV observations, we suggest that 9 of the 27 active regions were probably too weak to be predicted while on the far side. Overall, we conclude that HMI and GONG have similar reliability using the current data-processing procedures. 相似文献
683.
Two Skylark rockets carrying ion and R.F. electron probes, lithium and sodium vapourisers and proton precession magnetometers were launched from Woomera, Australia in November and December 1965 and made at least four encounters with sporadic E ionization. A magnetic field minimum was detected on only one of these encounters, and the minimum was found to be 2–3 km below the observed ion layer. The wind measurements deduced from observations of the vapour trails indicated that the sporadic E layer occurred in a region of ion divergence. 相似文献
684.
685.
Dr. A. Hall 《Mineralogy and Petrology》1990,41(2-4):185-197
Summary A suite of spilitic rocks from S.W. England has been analysed for 27 major and trace elements. Factor analysis was used to resolve the effects of primary magmatic variation and secondary spilitic alteration in determining the distribution of each element. The variation of REE, Nb, Zr, Fe, Ti, Sc and V is mainly attributed to igneous fractionation, whereas the variation of the other elements mainly reflects the results of spilitization. Spilitization is considered to be due to reaction between basalts and seawater soon after their original eruption, rather than the result of later regional metamorphism.
With 5 Figures 相似文献
Geochemie von Spiliten aus SW England: Eine statistische Annäherung
Zusammenfassung Spilitische Gesteine aus Südwest-England wurden auf 27 Haupt— und Spurenelemente untersucht.Faktorenanalysen wurden benützt, um zu unterscheiden, inwieweit die Variation einzelner Elemente durch primäre magmatische bzw. sekundäre Spilitisierungsprozesse bedingt ist. Die Verteilung der SEE, Nb, Zr, Fe, Ti, Sc und V wird hautsächlich von der magmatischen Fraktionierung, die der anderen Elemente von der spilitischen Alteration kontrolliert.Die Spilitisierung wird eher auf eine Reaktion der frisch eruptierten Basalte mit dem Meerwasser, als auf spätere regional-metamorphe Prozesse zurückgeführt.
With 5 Figures 相似文献
686.
J. Hansen M. Sato R. Ruedy P. Kharecha A. Lacis R. Miller L. Nazarenko K. Lo G. A. Schmidt G. Russell I. Aleinov S. Bauer E. Baum B. Cairns V. Canuto M. Chandler Y. Cheng A. Cohen A. Del Genio G. Faluvegi E. Fleming A. Friend T. Hall C. Jackman J. Jonas M. Kelley N. Y. Kiang D. Koch G. Labow J. Lerner S. Menon T. Novakov V. Oinas Ja. Perlwitz Ju. Perlwitz D. Rind A. Romanou R. Schmunk D. Shindell P. Stone S. Sun D. Streets N. Tausnev D. Thresher N. Unger M. Yao S. Zhang 《Climate Dynamics》2007,29(7-8):661-696
We carry out climate simulations for 1880–2003 with GISS modelE driven by ten measured or estimated climate forcings. An ensemble
of climate model runs is carried out for each forcing acting individually and for all forcing mechanisms acting together.
We compare side-by-side simulated climate change for each forcing, all forcings, observations, unforced variability among
model ensemble members, and, if available, observed variability. Discrepancies between observations and simulations with all
forcings are due to model deficiencies, inaccurate or incomplete forcings, and imperfect observations. Although there are
notable discrepancies between model and observations, the fidelity is sufficient to encourage use of the model for simulations
of future climate change. By using a fixed well-documented model and accurately defining the 1880–2003 forcings, we aim to
provide a benchmark against which the effect of improvements in the model, climate forcings, and observations can be tested.
Principal model deficiencies include unrealistically weak tropical El Nino-like variability and a poor distribution of sea
ice, with too much sea ice in the Northern Hemisphere and too little in the Southern Hemisphere. Greatest uncertainties in
the forcings are the temporal and spatial variations of anthropogenic aerosols and their indirect effects on clouds.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
687.
Sarah Marie Hall 《Area》2009,41(3):263-272
This paper addresses the difficulties and dilemmas that may occur when friendships are formed with participants during an ethnographic research project. The ongoing, reciprocal relationships developed with participants are considered essential in the data collection of ethnography, as an avenue through which research can be carried out. However, while friendships in the field may open new doors to research, they can also create new (ethical) challenges. This paper revisits these issues, alongside research ethics guidelines, using three different scenarios: the negotiation of methods of contact, the maintenance of contact with participants and the sharing of research diaries with participants. From these discussions, two issues arise that may have implications for future ethnographic research: the obstacle of social networking websites and the negotiation of appropriate research ethics when participants become our friends. 相似文献
688.
International Journal of Earth Sciences - Valleys are remarkably persistent features in many different tectonic settings, but the reasons for this persistence are rarely explored. Here, we examine... 相似文献
689.
690.
Nina Reuss Peter R. Leavitt Roland I. Hall Christian Bigler Dan Hammarlund 《Journal of Paleolimnology》2010,43(1):149-169
A surface-sediment survey of pigments in 100 lakes in the Scandes Mountains, northern Sweden, was combined with a reconstruction
of Holocene sedimentary pigments from Lake Seukokjaure to assess the major factors regulating phototrophic communities, and
how these controls may have changed during the period from the deglaciation (~9700 cal. years BP) to the present. The study
area covers a pronounced gradient of temperature and precipitation, and encompasses the subarctic tree line, an important
ecotonal boundary in this region. Lake Seukokjaure is located in a presently treeless basin close to the modern tree line.
The spatial survey of sedimentary pigments was analyzed using principle components analysis (PCA) and redundancy analysis
(RDA). PCA explained 73–83% of variance in pigment abundance and composition, whereas RDA explained 22–32% of variation in
fossil assemblages. Dissolved organic carbon (DOC) content of lake water, sediment δ13C, maximum lake depth, elevation and lake-water conductivity were all identified as environmental variables with significant
association with pigment abundances in the spatial survey, although phototrophic communities of lakes situated in different
vegetation zones (alpine, birch, conifer/birch) were incompletely distinguished by the ordinations. In the RDAs, the primary
pigment variability occurred along a production gradient that was correlated negatively to water-column DOC content and δ13C signature of sediments. This pattern suggested that the important controls of primary production were light regime and terrestrial
supplies of 13C-depleted carbon. In contrast, depth, elevation and conductivity were found to be more important for the differentiation
of the phototrophic community composition. Application of these spatial survey results to the Holocene sediment record of
Lake Seukokjaure demonstrated the importance of DOC for the temporal development of the lake, from an early state of high
production to a period of slight oligotrophication. In general, the algal changes were regulated by the interaction of DOC
and conductivity, although transitions in the phototrophic community during the late Holocene were less easily interpreted.
Terrestrial vegetation development thus appears to be of utmost importance for the regulation of primary production in oligotrophic
alpine and subarctic lakes and climate impacts on lakes, whereas other basin-specific factors may control the ontogeny of
algal community composition. 相似文献