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31.
T. E. Gergely 《Solar physics》1986,104(1):175-178
The relationship of moving type IV bursts and coronal mass ejections (CMEs) is of interest, because it may yield insights into the origin and the physics of the ejecta. We discuss the statistical association of moving type IV bursts and CMEs, and find that about one-third to one-half of the IVs occur in association with CMEs, while only about 5% of the CMEs are accompanied by moving type IVs. We also find that the mean speed of the moving IVs is smaller than the mean speed of CMEs, and conclude that the type IVs move out with the bulk of the ejecta.Proceedings of the Workshop on Radio Continua during Solar Flares, held at Duino (Trieste), Italy, 27–31 May, 1985. 相似文献
32.
The characteristics of a decameter type II burst associated with a possible behind-the-limb flare are discussed. The burst source had an unusually high velocity. Assuming that the disturbance propagated as an MHD wave, the magnetic field strength at the 40 MHz plasma level is estimated to be 5.6 gauss. 相似文献
33.
Recent observations of neutral line absorbing features in the solar atmosphere may give an important clue to the mechanism whereby both type III solar radiobursts and solar flares are triggered. It is suggested that as new satellite magnetic flux emerges at the edge of an active region in an area of opposite polarity a neutral sheet builds up between the new and old flux. When the sheet has a length of about a megametre its thermal insulation from the surrounding plasma is effective enough for a thermal instability to occur. The resulting compression and inflow of plasma is observed in H on the disc as a neutral line absorbing feature. Furthermore, the electric field of the accompanying collisionless tearing mode instability in a thin slab near the centre of the sheet exceeds the runaway field; it may therefore accelerate electrons to high enough energies to produce the type III burst which usually occurs at the same time as the absorbing feature. Perhaps the flare which sometimes ensues is triggered when the quasi-equilibrium state is destroyed by the development of turbulence in the neutral sheet. 相似文献
34.
Oliver?SchenkEmail author Janos?L.?Urai 《Contributions to Mineralogy and Petrology》2004,146(6):671-682
The effects of brine on recrystallization in halite are well known. However, properties of brine such as morphology, connectivity, diffusivity and the resulting influences on deformation mechanisms are still a matter of debate. This paper presents a microstructural study of dense, statically recrystallizing synthetic polycrystalline halite containing small amounts of brine. We used powders of two different grain size classes: <10 µm and 200–355 µm. The aggregates were compacted to brine-filled porosities less than about 2% and annealed at room temperature, without an external stress field.Coarse-grained samples undergo recrystallization manifested by the growth of large (up to 300 µm) strain-free grains into the deformed old grains. The new grains are frequently euhedral, with mobile grain boundaries moving at rates up to 6 nm/s. Their mobility is interpreted to be high due to the presence of water. Grain surfaces are smooth and the width of the water-rich zones is usually below the resolution of the SEM (less than 50 nm).The evolution of fine-grained samples starts with primary recrystallization and a reorganization of grain boundaries. After this stage, which lasts a few hours, normal grain growth effectively stops, and no significant increase of grain size is observed even after several months. Microstructural observations indicate contact healing at the grain boundaries, with dihedral angles ranging between 20 and 110°. We interpret these boundaries to be fluid-free, with the brine residing in a network of triple junction tubes. This system of triple junctions is interconnected and associated with significant permeability.While grain growth is inhibited in the fine-grained samples, after a few hours of annealing exaggerated grain growth is commonly initiated. This is manifested by the growth of large, euhedral grains replacing the fine-grained matrix. These grains also grow with low-index facets and their boundaries are also interpreted to be mobile due to the existence of a water-rich phase.Editorial Responsibility: J. Hoefs 相似文献
35.
Joyce Schmatz Oliver Schenk Janos L. Urai 《Contributions to Mineralogy and Petrology》2011,162(1):193-208
The distribution of fluids in grain boundaries, fluid inclusion morphology and kinetics have important effects on the evolution
of microstructure and transport properties and should be understood for correct interpretations for studies of thermobarometry
and paleorheology. We compare results of in situ annealing experiments on rock analogues in the presence of different pore
fluids in transmitted light: bischofite with saturated brine, camphor with ethanol, and camphor with ethylene glycol. The
solid–liquid systems vary in terms of wettability and solubility, while homologous temperatures, strain rates, annealing times,
and the initial textures are similar. In agreement with earlier work and theory, we observe different types of grain boundary–fluid
inclusion interaction at sufficiently low grain boundary velocity such as drag and drop, necking, and the break up into arrays
of smaller inclusions. In all three systems the maximum possible velocity of a fluid inclusion being dragged by a moving grain
boundary is dependent on the fluid inclusion size. We interpret this to reflect the fluid inclusion mobility, and compare
the trend with theoretical models which suggest that for all three systems the rate-limiting process is bulk diffusion and
not surface diffusion or solution-precipitation. 相似文献
36.
We have developed a new approach for the numerical modeling of deformation processes combining brittle fracture and viscous flow. The new approach is based on the combination of two meshless particle-based methods: the discrete element method (DEM) for the brittle part of the model and smooth particle hydrodynamics (SPH) for the viscous part. Both methods are well established in their respective application domains. The two methods are coupled at the particle scale, with two different coupling mechanisms explored: one is where DEM particles act as virtual SPH particles and one where SPH particles are treated like DEM particles when interacting with other DEM particles. The suitability of the combined approach is demonstrated by applying it to two geological processes, boudinage, and hydrofracturing, which involve the coupled deformation of a brittle solid and a viscous fluid. Initial results for those applications show that the new approach has strong potential for the numerical modeling of coupled brittle–viscous deformation processes. 相似文献
37.
Decametric storm radiation during the period July–August 1970 has been observed simultaneously with a high sensitivity spectrograph at Arecibo Observatory and with the log-periodic, swept-frequency array of the Clark Lake Radio Observatory. The observations complement each other; different types of fine structure emissions can be easily identified on the spectrograph records and their position can be determined from the swept-frequency recordings. We study the relative positions of the different emissions which have been observed during the storms. Four distinct sources appeared to be present. The continuum emission, the type I bursts and the flare-related type III's were all emitted at different locations. The storm type III bursts, type IIIb's and drift pairs overlapped in position, but appeared at different locations than the previously mentioned sources.On leave of absence from Instituto Argentino de Radioastronomia, Argentina. 相似文献
38.
39.
Novel prebiotic model systems: interactions of nucleosides and nucleotides with aqueous micellar sodium dodecanoate 总被引：1，自引：0，他引：1
Joseph Nagyvary Jack A. Harvey Faruk Nome Dan Armstrong Janos H. Fendler 《Precambrian Research》1976,3(6):509-516
The partition coefficients, K-values, of adenosine, guanosine, cytidine, uridine, 51-adenylic acid (AMP), 51-guanylic acid (GMP), 51-cytidylic acid (CMP), and 51-uridylic acid (UMP) between water and aqueous sodium dodecanoate has been determined by gel filtration on Sephadex G-25. Below the critical micelle concentration of the surfactant, K-values for all nucleotides and nucleosides are similar. Differential uptake of the four nucleotides and nucleosides is observed, however, by micellar sodium dodecanoate. K-values for adenosine, AMP; guanosine, GMP; cytidine, CMP; and uridine, UMP are 6.16·103, 9.52·103; 12.0·103, 14.6·103; 19.6·103, 19.6·103, 34.2·103 and 40.3·103. Similar K-values for corresponding pairs of nucleotides and nucleosides imply that the predominant interaction is between the pyrimidine or purine rings of the substrates and the charged Stern layer of the surfactant. Prebiotic significance of these results is discussed. 相似文献
40.
A study of the circular polarization structure of solar active regions has been made from data obtained at 3.5 mm wavelength, using the 36 ft diameter radio telescope of the National Radio Astronomy Observatory at Kitt Peak, Arizona. The angular resolution of the telescope at this wavelength is 1.2. All important active regions observed at 3.5 mm are bipolar in nature; the degree of polarization ranges from 1 to about 2%. These oppositely polarized components correspond with the Mt. Wilson magnetic regions of opposite polarity; the line of zero polarization delineates the neutral line between the regions of opposite polarity on magnetograms. The longitudinal magnetic fields at the level of 3.5 mm emission computed from the degree of polarization are found to be several hundred gauss. 相似文献