Using Strong Solar Coronal Emission Lines as Coronal Flux Proxies     

Falconer  David A.  Jordan  Stuart D.  Brosius  Jeffrey W.  Davila  Joseph M.  Thomas  Roger J.  Andreatta  Vicenzo  Hara  Hirohisa 《Solar physics》1998,180(1-2):179-191

We investigate the possibility that strong EUV lines observed with the Goddard Solar EUV Rocket Telescope and Spectrograph (SERTS) provide good proxies for estimating the total coronal flux over shorter wavelength ranges. We use coordinated SERTS and Yohkoh observations to obtain both polynomial and power-law fits relating the broad-band soft X-ray fluxes to the intensities of Fexvi 335 Ú and 361 Ú, Fexv 284 Ú and 417 Ú, and Mgix 368 Ú measured with SERTS. We found that the power-law fits best cover the full range of solar conditions from quiet Sun through active region, though not surprisingly the cooler Mgix 368 Ú line proves to be a poor proxy. The quadratic polynomial fits yield fair agreement over a large range for all but the Mgix line. However, the linear fits fail conspicuously when extrapolated into the quiet-Sun regime. The implications of this work for the Heii 304 Ú line formation problem are also briefly considered.  相似文献   

Sensitivity of frequency-dependent traveltimes to laterally heterogeneous, anisotropic Earth structure     

Li Zhao  & Thomas H. Jordan 《Geophysical Journal International》1998,133(3):683-704

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The Need for a Common Framework for Collection and Interpretation of Data in Platinum-Group Element Geochemistry     

Iain McDonald 《Geostandards and Geoanalytical Research》1998,22(1):85-91

Platinum-group element (PGE) concentrations and the distribution of the metals in rocks serve as important tracers of mantle processes, as well as extraterrestrial input into crustal environments, but common standards regarding the gathering and presentation of PGE data have never been formalized. Effective modelling assumes that concentration data are within acceptable levels of precision, yet the practices used in some studies to determine precision do not adequately assess precision and, as a result, the uncertainties on PGE concentrations and PGE ratios are sometimes consistently underestimated. This article argues that replicate analyses of unknowns must be adopted more widely in order to overcome this problem. Related to the issue of uncertainties on PGE concentrations, is the issue of uncertainty associated with normalisation. Arguments have recently been put forward as to the significance of small positive or negative anomalies on chondrite nor-malized plots. At least four CI chondrite PGE datasets (of varying age and quality) are currently used for normalisation and significantly different patterns can be derived simply by using one dataset rather than another. This article is intended to open a debate within the PGE research community by asking whether more consistency needs to be applied in PGE analysis and in the subsequent interpretation of data. A rigorous assessment of the real uncertainties on PGE concentrations and the adoption of a standard CI chondrite PGE dataset, in order to eliminate bias from normalisation, are suggested to be central to this.  相似文献   

Properties of pressure fluctuations in an atmospheric boundary layer     

John A. McDonald  Eugene Herrin 《Boundary-Layer Meteorology》1975,8(3-4):419-436

From experimental data it is shown that there is a relationship between measured wind speed and associated micropressure levels. It is also shown that turbulent eddies associated with the wind vanish within distances of five to six times their size, and that these eddies exhibit normal dispersion. These results confirm, at the atmospheric scales, results previously observed only in model experiments.  相似文献   

Erratum to: Variability of gas composition and flux intensity in natural marine hydrocarbon seeps     

Jordan F. Clark  Libe Washburn  Katherine Schwager Emery 《Geo-Marine Letters》2010,30(3-4):389-389

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Last interglacial climates of south-eastern Australia: plant and beetle-based reconstructions from Yarra Creek,King Island,Tasmania     

Nick Porch  Gregory J. Jordan  David M. Price  Richard W. Barnes  Mike K. Macphail  Mike Pemberton 《Quaternary Science Reviews》2009,28(27-28):3197-3210

This paper explores the palaeoclimatic significance of a fossil plant and insect record from Yarra Creek, on King Island, between Tasmania and the Australian mainland. The record dates, based upon a thermoluminescence chronology and other evidence, to Marine Isotope Stage 5 (MIS 5); the exact timing is impossible to ascertain given the resolution of the thermoluminescence results and the presence of an unconformity in the dated section. The presence of a cool-temperate rainforest flora, outside its modern range, and other independent evidence, suggest the sequence may represent the last interglacial (MIS 5e) rather than a later MIS 5 substage. Using coexistence methods that compare modern climatic ranges of the taxa in the assemblage we reconstruct independent beetle and plant based annual and seasonal temperate and precipitation parameters. The results imply the assemblage was deposited under a wetter summer climate and suggest conditions of enhanced temperature seasonality. It is probable that enhanced temperature seasonality is a methodological artefact reflecting the rarity of extremely equable climates (like King Island) in modern climate space. This would indicate a limitation of most methods of palaeoclimatic reconstruction that rely on modern datasets – it is only possible to reconstruct past climates as being within the range of values in that currently exist in modern climate space.  相似文献   

A spectral atlas of post-main-sequence stars in ω Centauri: kinematics, evolution, enrichment and interstellar medium     

Jacco Th. van Loon  Floor van Leeuwen  Barry Smalley  rew W. Smith  Nicola A. Lyons  Iain McDonald  Martha L. Boyer 《Monthly notices of the Royal Astronomical Society》2007,382(3):1353-1374

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O i line emission in cool stars: calculations using partial redistribution     

R. Koncewicz  C. Jordan 《Monthly notices of the Royal Astronomical Society》2007,374(1):220-231

Radiative transfer calculations have been performed for five cool stars: α Tau, β Gem, Procyon, ε Eri and the Sun, for the purpose of investigating the behaviour of the O  i emission over a wide range of stellar types, and its dependence on coherent photon scattering. These stars span a range of spectral types from F5 iv – v to K5 iii and surface gravities  1.25 < log  g * < 4.75  . Particular attention has been paid to the calculation of the flux in the resonance triplet around 1305 Å which is pumped by H Lyβ, including the effects of partial redistribution (PRD) and cross-redistribution of photons. These are the first calculations for the resonance triplet in giant stars using a full PRD treatment. Calculations of the predominantly collisionally excited intersystem doublet at 1355, 1358 Å are included, and it is found that the ratio of these fluxes shows the effects of opacity. The flux in the forbidden line at 1641 Å is calculated for the giant stars and the effects of coherent scattering on this line are investigated. The discrepancy between the calculated and observed fluxes in the O  i lines is used to infer the inadequacy of single-component chromospheric models.  相似文献   

Phosphorus Burial in Sediments Along the Salinity Gradient of the Patuxent River,a Subestuary of the Chesapeake Bay (USA)   总被引：2，自引：0，他引：2  

Jeanne L. Hartzell  Thomas E. Jordan  Jeffrey C. Cornwell 《Estuaries and Coasts》2010,33(1):92-106

We used a sequential extraction technique and ²¹⁰Pb dating to determine the chemical form and amount of particulate phosphorus (PP) that is retained during burial in 1-m-long sediment cores collected along a salinity gradient from tidal freshwater to the mesohaline waters of the Patuxent River, a subestuary of the Chesapeake Bay. PP buried in the study sites with salinity values ≤3 was similar in concentration and form to PP entering the Patuxent from the watershed, suggesting efficient sequestration by the sediments at these low-salinity sites. PP extracted with citrate–dithionite–bicarbonate was the dominant form of PP at all salinities and all depths, and organic-P was the second most abundant fraction. We estimated that 81% of PP entering from the watershed is trapped in the sediments of the upper Patuxent subestuary and that the subtidal sediments retain three times as much PP as the marshes adjacent to the study sites.  相似文献   

Mapping Energy: Cartographies of Energy Into The Twenty‐First Century     

Jordan P. Howell  David L. Baylis 《Geographical review》2014,104(2):209-228

“Energy” presents a number of complex and interrelated challenges regarding the environment, economy, and politics. In this paper, we argue that cartography should help clarify our understanding of energy issues, but ask whether this has in fact been the case. In a review of over 100 articles pulled from twenty‐three peer‐reviewed geography journals, we qualitatively assess energy maps published since the early 20^th century, examining trends in topic and cartographic technique. Energy maps in geography journals have focused on North America and Western Europe while relying on proportional symbols, grayscale production, and the analysis of energy phenomena at the national scale—tendencies that in many instances have limited our understanding of the ways in which energy is actually consumed. Simultaneously, cartographers are limited to the energy data available to them, frequently precluding small‐scale consumption analysis or consideration of diurnal and seasonal trends. We argue that the future of energy cartography relies on access to consumption data coupled with greater user interactivity.  相似文献