The Hα/Hβ ratio in solar flares     

Harold Zirin  Margaret Liggett  Alan Patterson 《Solar physics》1982,76(2):387-392

We have measured the ratio of H to H central intensities in the peak kernels of 14 flares, using simultaneous filtergrams. The ratio is typically one with some scatter. By contrast, in stellar flares the ratio is about 0.8.  相似文献   

The Es 511 Y Job Application Form: An Unconventional Data Source For The Study Of Disadvantaged Urban Migrants     

Shane Davies  Gary L. Flower 《The Professional geographer》1972,24(3):253-256

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Single crystal Mössbauer studies of 1M biotite     

Laurence P. Aldridge  James Finch  Graeme J. Gainsford  Kevin H. Patterson  W. Craighead Tennant 《Physics and Chemistry of Minerals》1991,17(7):583-590

Electric field gradient (EFG) measurements for Fe²⁺ in the cis- and trans-sites of a large single crystal of trioctahedral biotite of the lM polytype are described. Attempts to apply thickness and polarisation corrections are outlined. The measured EFG's are distinctly rhombic: = 0.28 and 0.42 respectively for the cis- and transsites and the EFG principal directions lie approximately along the crystallographic axes. For the cis-site V _y lies close to the normal to the basal plane while for the transsite lies close to this direction.  相似文献   

Evolution of magnetic fields and mass flow in a decaying active region     

Hongqi Zhang  Guoxiang AI  Haimin Wang  Harold Zirin  Alan Patterson 《Solar physics》1992,140(2):307-316

Five days of coordinated observation were carried out from 24–29 September, 1987 at Big Bear and Huairou Solar Observatories. Longitudinal magnetic fields of an p sunspot active region were observed almost continuously by the two observatories. In addition, vector magnetic fields, photospheric and chromospheric Doppler velocity fields of the active region were also observed at Huairou Solar Observatory. We studied the evolution of magnetic fields and mass motions of the active region and obtained the following results: (1) There are two kinds of Moving Magnetic Features (MMFs). (a) MMFs with the same magnetic polarity as the center sunspot. These MMFs carry net flux from the spot, move through the moat, and accumulate at the moat's outer boundary. (b) MMFs in pairs of mixed polarity. These MMFs are not responsible for the decay of the spot since they do not carry away the net flux. MMFs in category (b) move faster than those of (a). (2) The speed of the mixed polarity MMFs is larger than the outflow measured by photospheric Dopplergrams. The uni-polar MMFs are moving at about the same speed as the Doppler outflow. (3) The chromospheric velocity is in approximately the opposite direction from the photospheric velocity. The photospheric Doppler flow is outward; chromospheric flow is inward. We also found evidence that downward flow appears in the photospheric umbra; in the chromosphere there is an upflow.  相似文献   

Implementation of Particle-scale Rotation in the 3-D Lattice Solid Model     

Yucang Wang  Steffen Abe  Shane Latham  Peter Mora 《Pure and Applied Geophysics》2006,163(9):1769-1785

In this study, 3-D Lattice Solid Model (LSMearth or LSM) was extended by introducing particle-scale rotation. In the new model, for each 3-D particle, we introduce six degrees of freedom: Three for translational motion, and three for orientation. Six kinds of relative motions are permitted between two neighboring particles, and six interactions are transferred, i.e., radial, two shearing forces, twisting and two bending torques. By using quaternion algebra, relative rotation between two particles is decomposed into two sequence-independent rotations such that all interactions due to the relative motions between interactive rigid bodies can be uniquely decided. After incorporating this mechanism and introducing bond breaking under torsion and bending into the LSM, several tests on 2-D and 3-D rock failure under uni-axial compression are carried out. Compared with the simulations without the single particle rotational mechanism, the new simulation results match more closely experimental results of rock fracture and hence, are encouraging. Since more parameters are introduced, an approach for choosing the new parameters is presented.  相似文献   

Oligocene to Recent tectonic history of the Central Solomon intra-arc basin as determined from marine seismic reflection data and compilation of onland geology     

Shane Cowley  Paul Mann  M. F. Coffin  Thomas H. Shipley 《Tectonophysics》2004,389(3-4):267

Systematic analysis of a grid of 3450 km of multichannel seismic reflection lines from the Solomon Islands constrains the late Tertiary sedimentary and tectonic history of the Solomon Island arc and its convergent interaction with the Cretaceous Ontong Java oceanic plateau (OJP). The OJP, the largest oceanic plateau on Earth, subducted beneath the northern edge of the Solomon arc in the late Neogene, but the timing and consequences of this obliquely convergent event and its role in the subduction polarity reversal process remain poorly constrained. The Central Solomon intra-arc basin (CSB), which developed in Oligocene to Recent time above the Solomon arc, provides a valuable record of the tectonic environment prior to and accompanying the OJP convergent event and the subsequent arc polarity reversal. Recognition of regionally extensive stratigraphic sequences—whose ages can be inferred from marine sedimentary sections exposed onland in the Solomon Islands—indicate four distinct tectonic phases affecting the Solomon Island arc. Phase 1: Late Oligocene–Late Miocene rifting of the northeast-facing Solomon Island arc produced basal, normal-fault-controlled, asymmetrical sequences of the CSB; the proto-North Solomon trench was probably much closer to the CSB and is inferred to coincide with the trace of the present-day Kia-Kaipito-Korigole (KKK) fault zone; this protracted period of intra-arc extension shows no evidence for interruption by an early Miocene period of convergent “soft docking” of the Ontong Java Plateau as proposed by previous workers. Phase 2: Late Miocene–Pliocene oblique convergence of the Ontong Java Plateau at the proto-North Solomon trench (KKK fault zone) and folding of the CSB and formation of the Malaita accretionary prism (MAP); the highly oblique and diachronous convergence between the Ontong Java plateau and the Solomon arc terminates intra-arc extension first in the southeast (Russell subbasin of the CSB) during the Late Miocene and later during the Pliocene in the northwest (Shortland subbasin of the CSB); folds in the CSB form by inversion of normal faults formed during Phase 1; Phinney et al. [Sequence stratigraphy, structural style, and age of deformation of the Malaita accretionary prism (Solomon arc-Ontong Java Plateau convergent zone)] show a coeval pattern of southeast to northwest younging in folding and faulting of the MAP. Phase 3: Late Pliocene–early Pleistocene arc polarity reversal and subduction initiation at the San Cristobal trench. Effects of this event in the CSB include the formation of a chain of volcanoes above the subducting Australia plate at the San Cristobal trench, the formation of the broad synclinal structure of the CSB with evidence for truncation at the uplifted flanks, and widespread occurrence of slides and “seismites” (deposits formed by seismic shaking). Phase 4: Pleistocene to Recent continued shortening and synclinal subsidence of the CSB. Continued Australia-Pacific oblique plate convergence has led to deepening of the submarine, elongate basin axis of the synclinal CSB and uplift of the dual chain of the islands on its flanks.  相似文献   

Biotite composition as a tool for the identification of Quaternary tephra beds     

Phil Shane  Victoria SmithIan Nairn 《Quaternary Research》2003,59(2):262-270

Stratigraphically important Quaternary rhyolitic tephra deposits that erupted from the Okataina and Taupo volcanic centers in New Zealand can be geochemically identified using the FeO and MgO contents of their biotite phenocrysts. The FeO/MgO ratio in biotite does not correlate with FeO/MgO in the coexisting glass phase so that tephra beds with similar glass compositions can be discriminated by their different biotite compositions. Some individual tephra deposits display sequential changes in biotite composition that allow separate phases of the eruption to be identified, greatly increasing the potential precision for correlation. In addition, devitrified lavas that are unsuitable for glass analysis can be correlated to coeval tephra deposits by their biotite compositions. Biotite is common in high-K₂O (>4 wt%) tephra beds and is widely dispersed in ash plumes because of its platy form, thus making it important in correlation studies.  相似文献   

Author Index     

Andrew L. Macumber  R. Timothy Patterson  Lisa A. Neville  Hendrik Falck 《Journal of Paleolimnology》2003,29(4):511-511

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British retirees in Malta: components of the cross-national relationship     

Warnes AM  Patterson G 《International journal of population geography : IJPG》1998,4(2):113-133

"The paper focuses on three aspects of the retirement of British citizens to Malta and Gozo: the evolution of the British settlement, four pathways to the islands, and the formation of the current demographic and household characteristics.... The immigration of British retirees to Malta has fluctuated in volume and character over the last 35 years, partly in response to changes in Maltese fiscal and residence policies, and partly reflecting the changing demand for overseas retirement settlement in the UK. The substantial contribution of intercommunal married couples to the British retired resident population and the buoyancy of both tourist visits and new arrivals suggests that its size will at least be stable or will grow slowly for many decades to come."  相似文献   

Multiple Sources for Sea-Rafted Loisels Pumice, New Zealand     

Phil Shane  Paul Froggatt  Ian Smith  Murray Gregory 《Quaternary Research》1998,49(3):271-279

Sea-rafted Loisels Pumice is one of the few stratigraphic markers used to correlate late Holocene coastal deposits in New Zealand. Along with underlying sea-rafted products of the local Taupo eruption of ca. 1800 yr B.P., these events have been used to bracket the first arrival of humans at New Zealand. Loisels Pumice is dacitic to rhyolitic (SiO₂63–78 wt%) in composition, but individual clasts are homogeneous (SiO₂range ± 1 wt%). Characteristics include very low K₂O (0.5–1.75 wt%) and Rb (<25 ppm) and a mineralogy dominated by calcic and mafic xenocrysts. Similar features are shared by pumices of the Tonga–Kermadec arc, suggesting a common tholeiitic oceanic source. Interclast diversity of Loisels Pumice suggests that it is the product of several eruptive events from different volcanoes. The differences in glass and mineral compositions found at various sites can be explained if the deposits are from different events. A multisource origin can also partially explain the discrepancy in reported¹⁴C ages (ca. 1500–600 yr B.P.) from different localities. Therefore, the value of Loisels Pumice as a stratigraphic marker is questionable, and it does not constrain the arrival of humans. The predominant westward drift of historic Tonga–Kermadec arc pumices and prevailing ocean currents suggest a long anticlockwise semicircular transport route into the Tasman Sea before sea-rafted pumice arrival in New Zealand. The diversity of the pumices indicates that silicic eruptions frequently occur from the predominantly basic oceanic volcanoes.  相似文献