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191.
Proton Enhancements and Their Relation to the X-Ray Flares During the Three Last Solar Cycles 总被引:1,自引:0,他引:1
A.?Belov H.?Garcia V.?Kurt H.?MavromichalakiEmail author M.?Gerontidou 《Solar physics》2005,229(1):135-159
Energetic proton measurements obtained from the GOES and IMP-8 satellites as well as from ground-based neutron monitors are
compared with the GOES soft X-ray measurements of the associated solar flares for the period 1975–2003. The present study
investigates a broad range of phenomenology relating proton events to flares (with some references to related interplanetary
disturbances), including correlations of occurrence, intensities, durations and timing of both the particle event and the
flare as well as the role of the heliographic location of the designated active region. 1144 proton events of > 10 MeV energy
were selected from this 28-year period. Owing primarily to the low particle flux threshold employed more than half of this
number was found to be reliably connected with an X-ray flare. The statistical analysis indicates that the probability and
magnitude of the near-Earth proton enhancement depends critically on the flare's importance and its heliolongitude. In this
study all flares of X-ray importance > X5 and located in the most propitious heliolongitude range, 15∘W to 75∘W, were succeeded by a detectable proton enhancement. It was also found that the heliolongitude frequently determines the
character of the proton event time profile. In addition to intensity, duration and timing, proton events were found to be
related to the other flare properties such as lower temperatures and longer loop lengths. 相似文献
192.
A 1052-year tree-ring proxy for Alpine summer temperatures 总被引:6,自引:0,他引:6
Ulf Büntgen Jan Esper David C. Frank Kurt Nicolussi Martin Schmidhalter 《Climate Dynamics》2005,25(2-3):141-153
A June–August Alpine temperature proxy series is developed back to AD 951 using 1,527 ring-width measurements from living trees and relict wood. The reconstruction is composed of larch data from
four Alpine valleys in Switzerland and pine data from the western Austrian Alps. These regions are situated in high elevation
Alpine environments where a spatially homogenous summer temperature signal exists. In an attempt to capture the full frequency
range of summer temperatures over the past millennium, from inter-annual to multi-centennial scales, the regional curve standardization
technique is applied to the ring width measurements. Correlations of 0.65 and 0.86 after decadal smoothing, with high elevation
meteorological stations since 1864 indicate an optimal response of the RCS chronology to June–August mean temperatures. The
proxy record reveals warm conditions from before AD 1000 into the thirteenth century, followed by a prolonged cool period, reaching minimum values in the 1820s, and a warming
trend into the twentieth century. This latter trend and the higher frequency variations compare well with the actual high
elevation temperature record. The new central Alpine proxy suggests that summer temperatures during the last decade are unprecedented
over the past millennium. It also reveals significant similarities at inter-decadal to multi-centennial frequencies with large-scale
temperature reconstructions, however, deviating during certain periods from H.H. Lamb‘s European/North Atlantic temperature
history. 相似文献
193.
David A. H. Buckley Mark Cropper Kurt van der Heyden S. B. Potter Dayal T. Wickramasinghe 《Monthly notices of the Royal Astronomical Society》2000,318(1):187-194
We present polarimetric and spectroscopic observations of the ROSAT source RX J1141.3−6410, recently identified as a polar. The detection of circular polarization variations, with an amplitude of 10 per cent, over a 3.16-h period confirms that the system is a polar (AM Herculis star). Supporting evidence comes from the nature of the emission lines and their radial velocity variability. In addition, we observe continuum slope changes in the far-red spectral region (∼6000–8200 Å), indicative of phase dependent cyclotron emission. Polarimetric modelling at two wavelengths establishes RX J1141.3−6410 as a single-pole system, with i ∼ β ∼70°. The accretion region is extended in magnetic longitude, and is totally self-occulted for ∼25 per cent of the orbit. The radial velocity curves derived from the emission lines show a phasing with maximum blueshift occurring with Δ φ ∼0.05 of maximum intensity and circular polarisation. In addition, the broader component of the lines exhibit a substantial radial velocity phase shift with respect to the narrower component, in the sense that the broad component preceeds the narrow. This can be readily understood if the narrower component is principally a result of orbital motion of the stream material and the broad component mainly a result of streaming motion near the coupling region. The phasing of the Ca ii near-infrared line radial velocities also supports this general picture. 相似文献
194.
Sean F. Gallen Karl W. Wegmann Kurt L. Frankel Stephen Hughes Robert Q. Lewis Nathan Lyons Paul Paris Kristen Ross Jennifer B. Bauer Anne C. Witt 《地球表面变化过程与地形》2011,36(9):1254-1267
The southern Appalachians represent a landscape characterized by locally high topographic relief, steep slopes, and frequent mass movement in the absence of significant tectonic forcing for at least the last 200 Ma. The fundamental processes responsible for landscape evolution in a post‐orogenic landscape remain enigmatic. The non‐glaciated Cullasaja River basin of south‐western North Carolina, with uniform lithology, frequent debris flows, and the availability of high‐resolution airborne lidar DEMs, is an ideal natural setting to study landscape evolution in a post‐orogenic landscape through the lens of hillslope–channel coupling. This investigation is limited to channels with upslope contributing areas >2.7 km2, a conservative estimate of the transition from fluvial to debris‐flow dominated channel processes. Values of normalized hypsometry, hypsometric integral, and mean slope vs elevation are used for 14 tributary basins and the Cullasaja basin as a whole to characterize landscape evolution following upstream knickpoint migration. Results highlight the existence of a transient spatial relationship between knickpoints present along the fluvial network of the Cullasaja basin and adjacent hillslopes. Metrics of topography (relief, slope gradient) and hillslope activity (landslide frequency) exhibit significant downstream increases below the current position of major knickpoints. The transient effect of knickpoint‐driven channel incision on basin hillslopes is captured by measuring the relief, mean slope steepness, and mass movement frequency of tributary basins and comparing these results with the distance from major knickpoints along the Cullasaja River. A conceptual model of area–elevation and slope distributions is presented that may be representative of post‐orogenic landscape evolution in analogous geologic settings. Importantly, the model explains how knickpoint migration and channel–hillslope coupling is an important factor in tectonically‐inactive (i.e. post‐orogenic) orogens for the maintenance of significant relief, steep slopes, and weathering‐limited hillslopes. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
195.
Benjamin J.C. Laabs David W. Marchetti Jeffrey S. Munroe Kurt A. Refsnider John C. Gosse Elliott W. Lips Richard A. Becker David M. Mickelson Brad S. Singer 《Quaternary Research》2011,76(2):272-284
Understanding the timing of mountain glacier and paleolake expansion and retraction in the Great Basin region of the western United States has important implications for regional-scale climate change during the last Pleistocene glaciation. The relative timing of mountain glacier maxima and the well-studied Lake Bonneville highstand has been unclear, however, owing to poor chronological limits on glacial deposits. Here, this problem is addressed by applying terrestrial cosmogenic 10Be exposure dating to a classic set of terminal moraines in Little Cottonwood and American Fork Canyons in the western Wasatch Mountains. The exposure ages indicate that the main phase of deglaciation began at 15.7 ± 1.3 ka in both canyons. This update to the glacial chronology of the western Wasatch Mountains can be reconciled with previous stratigraphic observations of glacial and paleolake deposits in this area, and indicates that the start of deglaciation occurred during or at the end of the Lake Bonneville hydrologic maximum. The glacial chronology reported here is consistent with the growing body of data suggesting that mountain glaciers in the western U.S. began retreating as many as 4 ka after the start of northern hemisphere deglaciation (at ca. 19 ka). 相似文献
196.
The Athabasca Basin hosts many world-class unconformity-related uranium deposits. Recently, uranium reserves for the Eagle
Point basement-hosted deposit have increased with the discovery of new mineralized zones within secondary structures. A paragenetic
study of Eagle Point reveals the presence of three temporally distinct alteration stages: a pre-Athabasca alteration, a main
alteration and mineralization comprised of three substages, and a post-main alteration and mineralization stage that culminated
in remobilization of uraninite from primary to secondary structures. The pre-Athabasca alteration stage consists of minor
amounts of clinochlore, followed by dolomite and calcite alteration in the hanging wall of major fault zones and kaolinitization
of plagioclase and K-feldspar caused by surface weathering. The main alteration and uranium mineralization stage is related
to three temporally distinct substages, all of which were produced by isotopically similar fluids. A major early alteration
substage characterized by muscovite alteration and by precipitation Ca–Sr–LREE-rich aluminum phosphate-sulfate minerals, both
from basinal fluids at temperatures around 240°C prior to 1,600 Ma. The mineralization substage involved uraninite and hematite
precipitated in primary structures. The late alteration substage consists of dravite, uranophane-beta veins, calcite veins,
and sudoite alteration from Mg–Ca-rich chemically modified basinal fluids with temperatures around 180°C. The post-main alteration
and mineralization stage is characterized by remobilization of main stage uraninite from primary to secondary structures at
a minimum age of ca. 535 Ma. U–Pb resetting events recorded on primary and remobilized uraninites are coincident with fluid
flow induced by distal orogenies, remobilizing radiogenic Pb to a distance of at least 225 m above the mineralized zones. 相似文献
197.
The Vienna Basin Transfer Fault (VBTF) is a slow active fault with moderate seismicity (I
max~8–9, M
max~5.7) passing through the most vulnerable regions of Austria and Slovakia. We use different data to constrain the seismic
potential of the VBTF including slip values computed from the seismic energy release during the 20th century, geological data
on fault segmentation and a depth-extrapolated 3-D model of a generalized fault surface, which is used to define potential
rupture zones. The seismic slip of the VBTF as a whole is in the range of 0.22–0.31 mm/year for a seismogenic fault thickness
of 8 km. Seismic slip rates for individual segments vary from 0.00 to 0.77 mm/year. Comparing these data to geologically and
GPS-derived slip velocities (>1 mm/year) proofs that the fault yields a significant seismic slip deficit. Segments of the
fault with high seismic slip contrast from segments with no slip representing locked segments. Fault surfaces of segments
within the seismogenic zone (4–14 km depth) vary from 55 to 400 km2. Empirical scaling relations show that these segments are sufficiently large to explain both, earthquakes observed in the
last centuries, and the 4th century Carnuntum earthquake, for which archeo-seismological data suggest a magnitude of M ≥ 6. Based on the combination of all data (incomplete earthquake catalog, seismic slip deficits, locked segments, potential
rupture areas, indications of strong pre-catalog earthquakes) we argue, that the maximum credible earthquake for the VBTF
is in the range M
max = 6.0–6.8, significantly larger than the magnitude of the strongest recorded events (M = 5.7). 相似文献
198.
Boehnhardt Hermann Barucci Antonella Delsanti Audrey De Bergh Catherine Doressoundiram Alain Romon Jennifer Dotto Elisabetta Tozzi Gianpaolo Lazzarin Monica Fornasier Sonia Peixinho Nuno Hainaut Olivier Davies John Rousselot Philippe Barrera Luis Birkle Kurt Meech Karen Ortiz JoseLuis Sekiguchi Tomohiko Watanabe Jun-ichi Thomas Nick West Richard 《Earth, Moon, and Planets》2003,92(1-4):145-156
BVRI photometry of 107 TNOs and Centaurs establishes the range of spectral gradients to be between –5 to 55%/100 nm (with one exception). A cluster of very red Cubewanos is firmly identified in orbits of low inclination and eccentricity beyond 40 AU from the Sun. Further correlations between surface colours and dynamical parameters (inclination and perihelion distance) are suggested for Cubewanos and scattered disk objects, but lack complete confidence for their reality. Plutinos and Centaurs do not show any clear correlation between surface colours and orbital parameters. We present in this paper 12 spectra obtained in the visible region and nine of them for which we obtained also near infrared spectra up to 2.4 microns. A few other objects have been observed, but the data are still under reduction and analysis. The principal reported results obtained are: (i) a wide range of visible slopes; (ii) evidence for surface variations on 2001 PT13; and (iii) possible detection of few percent of water ice (1999 TC36}, 2000 EB173, 1999 DE9, 2001 PT13, 2000 QC243, 1998 SG35). 相似文献
199.
S. N. Kuznetsov V. G. Kurt I. N. Myagkova B. Yu. Yushkov K. Kudela 《Solar System Research》2006,40(2):104-110
The SONG instrument onboard the CORONAS-F satellite recorded gamma-ray emission with energy above 500 keV in 28 solar flares over three years of its in-orbit operation. According to the GOES classification, the X-ray importance of these flares lay within the range M1.4-X28. The gamma-ray energy recorded by SONG exceeded 4 MeV in 16 flares. Gamma-ray emission with energy up to 100 MeV was recorded in three events, more specifically, on August 25, 2001, October 28, 2003, and November 4, 2003. Increases in the count rate in the SONG channels that recorded neutrons with energies above 20 MeV were found during these three events. The energies of the recorded neutrons were estimated for the neutron increases. The time dependence of the neutron increases was compared with data from high-altitude ground-based neutron monitors that could, in principle, record the arrival of high-energy neutrons from the Sun. It should be noted that we detected series of flares with gamma-ray emission generated by the same active region (AR). The series in the last decade of August 2002 (AR NOAA 0069), the end of May 2003 (AR NOAA 0365), and the famous period of extreme solar activity in October–November 2003 associated with AR NOAA 0486 and AR NOAA 0501 are quite revealing. The catalog can be of use for future statistical and correlation analyses of solar flares. 相似文献
200.