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11.
Alastair S. Moore James Lazarus Matthias Hohenberger Joseph S. Robinson Edward T. Gumbrell Mike Dunne Roland A. Smith 《Astrophysics and Space Science》2007,307(1-3):139-145
We describe experiments that investigate the capability of an experimental platform, based on laser-driven blast waves created
in a medium of atomic clusters, to produce results that can be scaled to astrophysical situations. Quantitative electron density
profiles were obtained for blast waves produced in hydrogen, argon, krypton and xenon through the interaction of a high intensity
(I ≈ 1017 Wcm−2), sub-ps laser pulse. From this we estimate the local post-shock temperature, compressibility, shock strength and adiabatic
index for each gas. Direct comparisons between blast wave structures for consistent relative gas densities were achieved through
careful gas jet parameter control. From these we investigate the applicability of different radiative and Sedov-Taylor self-similar
solutions, and therefore the (ρ,T) phase space that we can currently access. 相似文献
12.
The solar wind flow behind shock fronts on June 25–26 and August 11, 1967 was studied using data from two spacecraft. For the last event the spacecraft were separated by 0.1 AU. In both cases there is a high degree of correlation between plasma parameters observed from the two spacecraft indicating that the features retain their identity over radial distances of at least 0.1 AU. 相似文献
13.
Coronal holes as sources of solar wind 总被引：3，自引：0，他引：3
J. T. Nolte A. S. Krieger A. F. Timothy R. E. Gold E. C. Roelof G. Vaiana A. J. Lazarus J. D. Sullivan P. S. McIntosh 《Solar physics》1976,46(2):303-322
We investigate the association of high-speed solar wind with coronal holes during the Skylab mission by: (1) direct comparison of solar wind and coronal X-ray data; (2) comparison of near-equatorial coronal hole area with maximum solar wind velocity in the associated streams; and (3) examination of the correlation between solar and interplanetary magnetic polarities. We find that all large near-equatorial coronal holes seen during the Skylab period were associated with high-velocity solar wind streams observed at 1 AU.Harvard College Observatory-Smithsonian Astrophysical Observatory.A substantial portion of this work was done while a visiting scientist at American Science and Engineering. 相似文献
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15.
Naomi W. Lazarus 《Geographical review》2016,106(3):360-380
This paper undertakes a risk assessment of coastal counties in the Gulf of Mexico impacted by the 2010 Deep Water Horizon oil spill. The study evaluates hazard risk from the perspective of community resilience, social capital, and access to resources. The proposed hazard risk location model re‐specifies risk as a function of hazard, exposure, and coping ability. The model employs an autoregressive function and a threshold analysis to develop a place‐based risk assessment. The results indicate that spatial variation in risk levels coincides with locational differences in social capital across the study area. Geographical proximity to the spill, population density, and unemployment rate are also key factors in determining overall risk. Furthermore, temporal variation in risk levels is determined by exposure to previous hazard events and changes in the business cycle. 相似文献
16.
Changes in magnetic-field and plasma data from Pioneer 6 across selected discontinuities are found to agree with those predicted for tangential discontinuities. Substantial velocity shears are found across the discontinuities, the largest observed being about 80 km/sec. From the observation of velocity shears and of the asymmetry in the orientation of tangential discontinuities, an East-West asymmetry in the solar-wind speed is inferred: Fast streams should tend to come from the West and slow streams from the East with respect to the average direction. This effect is discussed in relation to the rotation of the sun. 相似文献
17.
Lepping R.P. Berdichevsky D.B. Burlaga L.F. Lazarus A.J. Kasper J. Desch M.D. Wu C.-C. Reames D.V. Singer H.J. Smith C.W. Ackerson K.L. 《Solar physics》2001,204(1-2):285-303
The energetic charged particle, interplanetary magnetic field, and plasma characteristics of the `Bastille Day' shock and
ejecta/magnetic cloud events at 1 AU occurring over the days 14–16 July 2000 are described. Profiles of MeV (WIND/LEMT) energetic
ions help to organize the overall sequence of events from the solar source to 1 AU. Stressed are analyses of an outstanding
magnetic cloud (MC2) starting late on 15 July and its upstream shock about 4 hours earlier in WIND magnetic field and plasma
data. Also analyzed is a less certain, but likely, magnetic cloud (MC1) occurring early on 15 July; this was separated from
MC2 by its upstream shock and many heliospheric current sheet (HCS) crossings. Other HCS crossings occurred throughout the
3-day period. Overall this dramatic series of interplanetary events caused a large multi-phase magnetic storm with min Dst lower than −300 nT. The very fast solar wind speed (≥ 1100 km s−1) in and around the front of MC2 (for near average densities) was responsible for a very high solar wind ram pressure driving
in the front of the magnetosphere to geocentric distances estimated to be as low as ≈ 5 R
E, much lower than the geosynchronous orbit radius. This was consistent with magnetic field observations from two GOES satellites
which indicated they were in the magnetosheath for extended times. A static force-free field model is used to fit the two
magnetic cloud profiles providing estimates of the clouds' physical and geometrical properties. MC2 was much larger than MC1,
but their axes were nearly antiparallel, and their magnetic fields had the same left-handed helicity. MC2's axis and its upstream
shock normal were very close to being perpendicular to each other, as might be expected if the cloud were driving the shock
at the time of observation. The estimated axial magnetic flux carried by MC2 was 52×1020 Mx, which is about 5 times the typical magnetic flux estimated for other magnetic clouds in the WIND data over its first
4 years and is 17 times the flux of MC1. This large flux is due to both the strong axially-directed field of MC2 (46.8 nT
on the axis) and the large radius (R
0=0.189 AU) of the flux tube. MC2's average speed is consistent with the expected transit time from a halo-CME to which it
is apparently related. 相似文献
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Abstract Project-based emission reduction or ‘offset’ programs are being implemented widely, from the CDM (Clean Development Mechanism) to corporate voluntary efforts and municipal and state-level activities. Additionality assessment remains a central and persistent challenge in all programs. Concerns have been raised with methods currently used, such as investment analysis, barrier analysis, and performance thresholds. They have been variously critiqued for high costs, resistance to standardization, weak environmental integrity, and susceptibility to gaming. Technology penetration rates provide another means to infer additionality, and could be a potentially useful complement to other methods. The notion is that emerging technologies with low but increasing penetration rates typically require some type of support, as might be provided through offsets markets, to compete effectively in the marketplace. For penetration rate analysis to provide a useful tool for additionality assessment, several fundamental questions need to be addressed. What do penetration rates represent and how can they be measured? How can additionality evaluation utilize penetration rates? For which sectors and project types are the use of penetration rates most promising? This article shows that penetration tests have a mixture of pluses and minuses, with greater relevance in certain market niches and regions. Reasonable ranges for penetration thresholds are discussed, along with partial crediting approaches to reduce ‘knife-edge’ effects. 相似文献
20.
Granitic regolith, developed in the Boulder Creek catchment and adjacent areas, records a history of deep weathering, some of which may predate Quaternary time. Field and well-log measurements of weathering, chemical denudation and rates of erosion derived from 10Be cosmogenic radionuclide (CRN) data help to quantify rates of landscape change in the post-orogenic Rocky Mountains. The density of oxidized, fractured bedrock ranges from 2.7 to about 2.2 g cm− 3, saprolite and grus have densities between 2.0 and 1.8 g cm− 3, and 30 soil samples averaged 1.6 ± 0.2 g cm− 3. Highly weathered regolith in 540 wells averages 3.3 m thick, mean depth to bedrock in 1661 wells is 7 m, and the weathered thickness exceeds 10 m in relatively large local areas east of the late Pleistocene glacial limit. Thickness of regolith shows no simple relationship to rock type or structure, local slope, or distance from channels. Catchments in the vicinity of the Boulder Creek have an average CRN erosion rate of 2.2 ± 0.7 cm kyr− 1 for the past 10,000 to 40,000 yr. Annual losses of cations and SiO2 vary from about 2 to 5 g m− 2 over a runoff range of 10 to nearly 160 cm.Using measured rates in simple box models shows that if a substantial fraction of void space is created by volume expansion in the weathering rock materials, 7 m of weathered rock materials could form in as little as 230 kyr. If density loss results mainly from chemical denudation and some volume expansion, however, the same weathering profile would take > 1340 kyr to form. Rates of erosion measured by CRN could be balanced by the rate of soil formation from saprolite if the annual solute loss from soil is 2.0 g m− 2 and 70% of the density decrease from saprolite to grus and soil results from strain. Saprolite, however, forms from oxidized bedrock at a far slower rate and rates of saprolite formation cannot balance soil and grus losses to erosion. The zone of thick weathered regolith is likely an eroding relict landscape. The undulating surface marked by relatively low relief and tors is not literally a topographic surface of Eocene, Oligocene or Miocene age unless it was covered with deposits that were removed in Pliocene or Quaternary time. 相似文献