Effects of atmospheric oscillations on the field-aligned ion motions in the polar F-region     

S. Oyama  S. Nozawa  S. C. Buchert  M. Ishii  S. Watari  E. Sagawa  W. Kofman  J. Lilensten  R. Fujii 《Annales Geophysicae》2000,18(9):1154-1163

The field-aligned neutral oscillations in the F-region (altitudes between 165 and 275 km) were compared using data obtained simultaneously with two independent instruments: the European Incoherent Scatter (EISCAT) UHF radar and a scanning Fabry-Perot interferometer (FPI). During the night of February 8, 1997, simultaneous observations with these instruments were conducted at Tromsø, Norway. Theoretically, the field-aligned neutral wind velocity can be obtained from the field-aligned ion velocity and by diffusion and ambipolar diffusion velocities. We thus derived field-aligned neutral wind velocities from the plasma velocities in EISCAT radar data. They were compared with those observed with the FPI (=630.0 nm), which are assumed to be weighted height averages of the actual neutral wind. The weighting function is the normalized height dependent emission rate. We used two model weighting functions to derive the neutral wind from EISCAT data. One was that the neutral wind velocity observed with the FPI is velocity integrated over the entire emission layer and multiplied by the theoretical normalized emission rate. The other was that the neutral wind velocity observed with the FPI corresponds to the velocity only around an altitude where the emission rate has a peak. Differences between the two methods were identified, but not completely clarified. However, the neutral wind velocities from both instruments had peak-to-peak correspondences at oscillation periods of about 10–40 min, shorter than that for the momentum transfer from ions to neutrals, but longer than from neutrals to ions. The synchronizing motions in the neutral wind velocities suggest that the momentum transfer from neutrals to ions was thought to be dominant for the observed field-aligned oscillations rather than the transfer from ions to neutrals. It is concluded that during the observation, the plasma oscillations observed with the EISCAT radar at different altitudes in the F-region are thought to be due to the motion of neutrals.  相似文献   

Evidence for pre-seismic crustal movement in China and Japan     

Lide Cao  Yoichiro Fujii 《地学学报》1989,1(6):583-587

Some recent Chinese observations on precursory crustal movements detected by geodetic measurements such as short-range levelling or base-line survey across the active fault corroborate the three gamma phases model of Fujita and Fujii: Gamma 1 phase is pre-slip along the imminent faulting, gamma 2 is coseismic slip and gamma 3 is post-slip along the main or subsidiary faulting after an earthquake. Typical of these are the results of short-range levelling across the earthquake fault that ruptured during the 1976 Tangshan earthquake (M_s= 7.8). Associated with the occurrence of the Tangshan earthquake or the subsequent Ninghe earthquake (M_s= 6.9), remarkable gamma 2 phases were observed. At this same location abnormal gamma 1 or gamma 3 phases were detected from the Lulong 1982 earthquake (M_s= 6.2) that originated from the north end of the Tangshan Fault and was one of the aftershocks of the Tangshan earthquake. These phases are interpreted by analogy with the recent experimental results of stick-slip motion of the frictional sliding of rock.  相似文献   

Characterization of the Mefjell plutonic complex from the Sør Rondane Mountains, East Antarctica: Implications for the petrogenesis of Pan-African plutonic rocks of East Gondwanaland     

Zilong  Li  Yoshiaki  Tainosho  Jun-Ichi  Kimura  Kazuyuki  Shiraishi 《Island Arc》2005,14(4):636-652

Abstract The Mefjell plutonic complex consists of 500–550‐Ma Pan‐African plutonic rocks, which intrude into the Precambrian crystalline basement in the Sør Rondane Mountains, East Antarctica, and forms part of the Sør Rondane Suture Zone. The complex comprises syenitic and granitic (mostly monzogranitic) rocks, and is characterized by the presence of iron‐rich hydrous mafic minerals and primary ilmenite, both of which imply its formation at high temperature and under low oxygen fugacity conditions. The syenitic rocks are metaluminous, and are high in alkalis, K₂O/Na₂O, Al₂O₃, FeO_t/(FeO_t + MgO) (0.88–0.98), K/Rb (800–1000), Ga (18–28 p.p.m.), Zr (up to 2100 p.p.m.) and Ba. They also have a low Mg? (Mg/[Mg + Fe²⁺]), Rb, Sr, Nb, Y and F, low to moderate light rare earth element (LREE)/heavy rare earth element (HREE) ratios and positive Eu anomalies in their rare earth element (REE) patterns. The granitic rocks are metaluminous to peraluminous, and have a high Rb content, high Sr/Ba and LREE/HREE ratios, low K/Rb and negative Eu anomalies. Most of the syenitic and granitic rocks have Y/Nb ratios greater than 1.2, and are depleted in Nb, Ti and Sr on the primitive mantle‐normalized spider diagrams, indicating a crustal origin with subduction zone signatures. We interpret both the syenitic and granitic rocks to be derived from an iron‐rich lower crustal source by dehydration melting induced by the heat of mantle‐derived basaltic intrusion, after which they then underwent limited fractional crystallization. The Mefjell plutonic complex has a high Zr content and tectonic discrimination diagram signatures indicative of normal A‐type granitic rocks. Both rock suites may have been generated under the same postorogenic tectonic setting. The Mefjell syenitic rocks are chemically comparable to charnockites in the Gjelsvikjella and western Mühlig‐Hofmannfjella areas of East Antarctica, whereas the granitic rocks are comparable to aluminous A‐type granitic rocks in South India, which were emplaced during formation and evolution of the Gondwanaland supercontinent.  相似文献   

The petrology of ultramafic xenoliths from Summit Lake,near Prince George,British Columbia     

Mark Brearley  Christopher M. Scarfe  Toshitsugu Fujii 《Contributions to Mineralogy and Petrology》1984,88(1-2):53-63

Approximately 200 upper mantle xenoliths from Summit Lake, near Prince George, British Columbia, were collected from a basanitoid flow of Late Cenozoic (possibly post-glacial) age. The most abundant xenolith is spinel lherzolite (55%), with subordinate wehrlite (22%), clinopyroxenite (10%), olivine websterite (10%), websterite (2%) and dunite (1%). Xenoliths have granular textures and both green chrome diopside-bearing and black aluminous augitebearing xenoliths are present. About 5% of the xenoliths are banded on a cm scale, suggesting that the upper mantle beneath north-central British Columbia is heterogeneous on a scale of cm to meters.Microprobe data on the mineral phases indicate that the xenoliths are generally well equilibrated. Typically in spinel lherzolite, olivines are Fo₈₉, orthopyroxenes are En₉₀ and chrome diopside is Wo₄₅En₅₀Fs₅. Spinels vary in composition from xenolith to xenolith. The evidence for partial melting observed in five xenoliths, may be due to heating during incorporation of the xenoliths within the host magma or to instability caused by decompression as the xenoliths are transported to the surface.Using element partition geothermometers, equilibration temperatures are calculated to be between 1080–1100° C. Pressures, estimated from a Cordilleran geotherm, are between 18–20 kbar. These temperatures are somewhat higher than estimates from xenoliths from other localities in Late Cenozoic alkali basalts in south and central British Columbia. It is concluded, therefore, that either the Summit Lake suite represents samples from a deeper source region in the upper mantle or the Late Cenozoic geotherm varied in time and space.On leave from the Geological Institute, University of Tokyo  相似文献   

Melting relations of a magnesian abyssal tholeiite and the origin of MORBs     

Toshitsugu Fujii  Henri Bougault 《Earth and Planetary Science Letters》1983,62(2):283-295

Melting relations of a glassy magnesian olivine tholeiite from the FAMOUS area have been studied within the pressure range 1 atm to 15 kbar. From 1 atm to 10 kbar, olivine is the liquidus phase, followed by plagioclase and Ca-rich clinopyroxene. Above 10 kbar, Ca-rich clinopyroxene appears on the liquidus, followed by orthopyroxene and spinel. Near 10 kbar, olivine, orthopyroxene, clinopyroxene, spinel and plagioclase crystallize within 10°C of the liquidus. This indicates that a liquid of this magnesian olivine tholeiite composition could coexist with mantle peridotite at about 10 kbar. This result is in agreement with the geochemistry of Ni; the Ni concentration of the studied sample corresponds to the theoretical concentration in a primary magma [14,15].These data suggest that at least some magnesian mid-oceanic ridge basalts (MORBs) could be primary melts segregated from the mantle at depths near the transition zone between plagioclase lherzolite and spinel lherzolite (about 10 kbar). Based on this model, the residual mantle after extraction of MORBs should be lherzolite, not harzburgite.High-pressure (7–10 kbar) fractionation models involving olivine, plagioclase and clinopyroxene, which have been proposed by several workers (e.g. [36]) to explain the varieties of MORBs, were re-emphasized based on this melting study. The rare occurrence of clinopyroxene as a phenocryst phase in MORBs is explained by precipitation in a magma chamber at high pressure, or by dissolution of clinopyroxene formed earlier at high pressure.  相似文献   

The relationship between molecular composition and fluorescence properties of humic substances     

M. Ateia  J. Ran  M. Fujii  C. Yoshimura 《International Journal of Environmental Science and Technology》2017,14(4):867-880

The quantity and quality of dissolved organic matters have been widely characterized by fluorescence spectroscopy, yet the relationship between the fluorescence properties of dissolved organic matters and its molecular composition remains poorly described in the literature. Here, we measured the fluorescence excitation–emission matrix of 17 well-characterized humic substance standards to determine a range of fluorescence parameters, including classical fluorescence indices (e.g., fluorescence index, biological index and humification index) and parameters derived from parallel factor analysis (e.g., component contribution). Relationships between humic substance’s fluorescence and compositional parameters were then statistically examined using canonical correspondence and simple correlation analyses. The canonical correspondence analysis generally suggested that most fluorescence parameters determined here are highly associated with the amount of aliphatic and aromatic compounds in humic substances. However, the correlation analysis between single molecular and fluorescence parameters indicated that the fluorescence properties of humic substances including the parallel factor analysis component contribution also significantly correlate well with several aspects of the molecular composition of humic substances, such as elemental composition, carbon species, acidic functional group and iron complexation. Overall, our results suggest that measurement of humic substance’s fluorescence is beneficial in understanding the molecular composition and environmental functions of dissolved organic matters in natural and engineered waters.  相似文献   

Development of a new operational system for monitoring and forecasting coastal and open-ocean states around Japan     

Hirose  Nariaki  Usui  Norihisa  Sakamoto  Kei  Tsujino  Hiroyuki  Yamanaka  Goro  Nakano  Hideyuki  Urakawa  Shogo  Toyoda  Takahiro  Fujii  Yosuke  Kohno  Nadao 《Ocean Dynamics》2019,69(11):1333-1357

We developed a new system to monitor and forecast coastal and open-ocean states around Japan for operational use by the Japan Meteorological Agency. The system consists of an eddy-resolving analysis model based on four-dimensional variational assimilation and a high (2-km) resolution forecast model covering Japanese coastal areas that incorporates an initialization scheme with temporal and spatial filtering. Assimilation and forecast experiments were performed for 2008 to 2017, and the results were validated against various observation datasets. The assimilation results captured well the observed variability in sea surface temperature, coastal sea level, volume transport, and sea ice. Furthermore, the volume budget for the Japan Sea was significantly improved by the use of the 2-km resolution forecast model compared with the 10-km resolution analysis model. The forecast results indicate that this system has a predictive limit longer than 1 month in many areas, including in the Kuroshio current area south of Japan and the southern Japan Sea. In the forecast results of case studies, the 2017 Kuroshio large meander was well predicted, and warm water intrusions accompanying Kuroshio path variations south of Japan were also successfully reproduced. Sea ice forecasts for the Sea of Okhotsk largely captured the evolution of sea ice in late winter, but sea ice in early winter included relatively large errors. This system has high potential to meet operational requirements for monitoring and forecasting ocean phenomena at both meso- and coastal scales.

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