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61.
A database combining information about solar proton enhancements (SPEs) near the Earth and soft X-ray flares (GOES measurements)
has been used for the study of different correlations through the period from 1975 to May 2006. The emphasis of this work
is on the treatment of peak-size distributions of SXR flares and SPEs. The frequency of SXR flares and solar proton events
(>10 and >100 MeV, respectively) for the past three solar cycles has been found to follow mainly a power-law distribution
over three to five orders of magnitude of fluxes, which is physically correct beyond the “sensitivity” problem with the smallest
peak values. The absence of significant spectral steepening in the domain of the highest peak values demonstrates that during
the period considered, lasting 30 years, the limit of the highest flare’s energy release has not yet been achieved. The power-law
exponents were found to be −2.19±0.04, −1.34±0.02, and −1.46±0.04, for the total SXR flare distribution and the total SPE
distributions (for both E
P>10 MeV and E
P>100 MeV), respectively. For SPEs associated with flares located to the West of 20° W, the exponents are −1.22±0.05 (E
P>10 MeV) and −1.26±0.03 (E
P>100 MeV). The size distribution for corresponding flares follows a power law with a slope of −1.29±0.12. Thus, X-ray and
proton fluxes produced in the same solar events have very similar distribution shapes. Moreover, the derived slopes are not
incompatible with a linear dependence between X-ray flare power and proton fluxes near the Earth. A similar statistical relation
is obtained independently from the direct comparison of the X-ray and proton fluxes. These all argue for a statistically significant
relationship between X-ray and proton emissions. 相似文献
62.
Kurt Liffman 《Astrophysics and Space Science》2007,311(1-3):69-74
We discuss the star-disk electric circuit for a young stellar object (YSO) and calculate the expected torques on the star
and the disk. We obtain the same disk magnetic field and star-disk torques as given by standard magnetohydrodynamic (MHD)
analysis. We show how a short circuit in the star-disk electric circuit may produce a magnetically-driven jet flow from the
inner edge of a disk surrounding a young star.
An unsteady bipolar jet flow is produced that flows perpendicular to the disk plane. Jet speeds of order hundreds of kilometers
per second are possible, while the outflow mass loss rate is proportional to the mass accretion rate and is a function of
the disk inner radius relative to the disk co-rotation radius. 相似文献
63.
64.
In the Kor-, Saualpe and Pohorje regions of the Eastern Alps eclogite bodies occur within metapelitic gneisses. The bodies are between 1 meter and several hundreds of meters in size and some of them were defined by Haüy (1822) as the type locality for the rock type “eclogite”. A growing body of petrological work has documented the metamorphic evolution of the metapelites surrounding the eclogites. However, few phase diagrams have been constructed for the eclogite bodies themselves. Here we use recently available activity models for amphiboles to present new thermodynamic pseudosections for the Hohl locality of the Koralpe eclogites. We show that this eclogite reached peak conditions in a narrow PT field obliquely oriented in PT space between 16.5 and 20.5 kbar and 620°C to 720°C and that its metamorphic evolution was likely to have occurred under water saturated conditions. We conclude that eclogite and the surrounding metapelites have certainly undergone the same metamorphic peak in Eo-alpine time. Comparison of our results with different PT estimates on the eclogite from Pohorje, suggest that a PT gradient from Koralpe to Pohorje is likely. 相似文献
65.
Sulfide oxidizing bacterial mats are common in regions of the continental shelves characterized by high primary production and the resultant oxygen minimum zone. These mats are made up of several species of Beggiatoa and/or Thioploca, which oxidize sulfide that is generated in the sediment. Thioploca spp. inhabit a large polysaccharide sheath that encompasses bundles of 1–20 filaments (trichomes), each ranging from 3 to 60 μm in diameter. This sheath has been shown to be a critical component of the autecology of Thioploca. Analysis of Thioploca from cold seeps in Monterey Bay using light and transmission electron microscopy identified new and diverse microbial assemblages associated with interstitial spaces between trichomes, inside the sheath. Small diameter, non‐vacuolate, filamentous prokaryotes were numerous. Amoebae, euglenozoa, ciliates and other protists of unknown affiliation were observed in sheaths. Most of the protists possessed food vacuoles and some protists showed ultrastructural evidence of endosymbionts. These observations suggest that Thioploca sheaths may serve as oases on the sea floor, providing nutritional and detoxification services to previously unrecognized microbial partners. 相似文献
66.
Arnold J. H. Reesink Philip J. Ashworth Gregory H. Sambrook Smith James L. Best Daniel R. Parsons Mario L. Amsler Richard J. Hardy Stuart N. Lane Andrew P. Nicholas Oscar Orfeo Steven D. Sandbach Christopher J. Simpson Ricardo N. Szupiany 《Sedimentology》2014,61(4):1055-1085
To date, published studies of alluvial bar architecture in large rivers have been restricted mostly to case studies of individual bars and single locations. Relatively little is known about how the depositional processes and sedimentary architecture of kilometre‐scale bars vary within a multi‐kilometre reach or over several hundreds of kilometres downstream. This study presents Ground Penetrating Radar and core data from 11, kilometre‐scale bars from the Río Paraná, Argentina. The investigated bars are located between 30 km upstream and 540 km downstream of the Río Paraná – Río Paraguay confluence, where a significant volume of fine‐grained suspended sediment is introduced into the network. Bar‐scale cross‐stratified sets, with lengths and widths up to 600 m and thicknesses up to 12 m, enable the distinction of large river deposits from stacked deposits of smaller rivers, but are only present in half the surface area of the bars. Up to 90% of bar‐scale sets are found on top of finer‐grained ripple‐laminated bar‐trough deposits. Bar‐scale sets make up as much as 58% of the volume of the deposits in small, incipient mid‐channel bars, but this proportion decreases significantly with increasing age and size of the bars. Contrary to what might be expected, a significant proportion of the sedimentary structures found in the Río Paraná is similar in scale to those found in much smaller rivers. In other words, large river deposits are not always characterized by big structures that allow a simple interpretation of river scale. However, the large scale of the depositional units in big rivers causes small‐scale structures, such as ripple sets, to be grouped into thicker cosets, which indicate river scale even when no obvious large‐scale sets are present. The results also show that the composition of bars differs between the studied reaches upstream and downstream of the confluence with the Río Paraguay. Relative to other controls on downstream fining, the tributary input of fine‐grained suspended material from the Río Paraguay causes a marked change in the composition of the bar deposits. Compared to the upstream reaches, the sedimentary architecture of the downstream reaches in the top ca 5 m of mid‐channel bars shows: (i) an increase in the abundance and thickness (up to metre‐scale) of laterally extensive (hundreds of metres) fine‐grained layers; (ii) an increase in the percentage of deposits comprised of ripple sets (to >40% in the upper bar deposits); and (iii) an increase in bar‐trough deposits and a corresponding decrease in bar‐scale cross‐strata (<10%). The thalweg deposits of the Río Paraná are composed of dune sets, even directly downstream from the Río Paraguay where the upper channel deposits are dominantly fine‐grained. Thus, the change in sedimentary facies due to a tributary point‐source of fine‐grained sediment is primarily expressed in the composition of the upper bar deposits. 相似文献
67.
Fractional abundances of stratospheric negative ions are for the first time explicitly reported. The measurements made by balloon-borne ion mass spectrometers also rely on recent studies of electric field induced collisional dissociation of negative cluster ions conducted at our laboratory. These indicate that the negative ion composition measurements around 36 km conducted by our group do not suffer from any significant dissociation. The new composition data support ion identifications NO3?(HNO3)b and HSO4?(H2SO4)c(HNO3)d and the underlying ion reactions propo previously. Moreover, it is found that HSO4?(H2SO4)g-ions appear to be particularly stable and that H2SO4-association is very fast. Implications of the ion composition data for ion processes are discussed. 相似文献
68.
This paper develops a wide-band multi-spectral space for color representation with Aitken PCA algorithm. This novel mathematical space using the broad-band spectra matching method aims at improving the accuracy of color representation as well as reducing costs for processing and storing multi-spectral images. The results show that the space can present our experimental original spectral spaces (i. e. Munsell color matt and DIN-6164 color chips) with high efficiency, and that the spanning space with three eigenvectors can present the original space at more than 98% CSCR, and when 5 eigenvectors are used it can cover almost the whole original spaces. 相似文献
69.
Fossil particle tracks and spallation-produced He and Ne in the Kenna ureilite indicate that it existed in space as a small object for 23 m.y. In our study of Kenna, we found no evidence of trapped He or Ne. Large amounts of heavy rare gases occur in Kenna in concentrations typical of ureilites. In a step-wise release of gases, the isotopic compositions of Kr and Xe were found to be constant above 600°C, revealing the presence of a single retentively sited component. The Xe isotopic abundances are characterized by 124:126:128:129:130:131:132:134:136 = 0.471:0.414:8.280:103.61: 16.296:81.92:100:37.70:31.23. This isotopic composition is distinct from AVCC (average carbonaceous chondritic), but similar to compositions known for some time in certain temperature fractions of Renazzo, Murray and Murchison. Kenna-type Xe appears to be one of the several components found in carbonaceous chondrites.
Binz et al. (Geochim. Cosmochim. Acta 39, 1576–1579, 1975) have recently found that many volatile trace elements are strongly depleted in ureilites. Thus, the relatively large amounts of heavy rare gases present in ureilites did not result from a mixture of a volatile-rich component with the ureilite host. It appears that some material rich in carbon and heavy rare gases was incorporated into a differentiated ureilite host. All current hypotheses which purport to explain the origin of trapped gases in meteorites encounter difficulty in accounting for trapped gases in ureilites in a straightforward manner. 相似文献
70.
Arnold H. Bouma James M. Coleman Charles E. Stelting Barry Kohl 《Geo-Marine Letters》1989,9(3):161-170
A conceptual sea-level-driven depositional model for individual fanlobes (channel-overbank systems) of the Mississippi Fan
does not permit direct application of the sequence stratigraphic principles of Vail and colleagues. Deep Sea Drilling Project
Leg 96 results suggest that, during initial relative lowering of sea level, the canyon and upper fan channel were formed;
excavated fine-grained slope sediments may have formed a debris flow deposit base for the fanlobe. Continued lowering produced
constructional channel-levee-overbank deposits. Rising relative sea level inhibited input of coarse clastics, and channel
depressions filled with muds. A blanket of (hemi)pelagics represents relative high sea level stand. 相似文献