The response of the mid-latitude thermospheric wind to magnetic activity     

T. Yagi  P.L. Dyson 《Planetary and Space Science》1985,33(4):461-467

Observations of the thermospheric wind at a mid-latitude station have been made using a Fabry-Perot interferometer to measure the Doppler shift of the nighttime OI emission at 630 nm. The results from 12 summer nights show that the zonal wind has a distinct feature associated with magnetic activity. The zonal wind first reverses and becomes westward. The maximum strength of the westward wind, its duration, and the maximum strength of the subsequent eastward wind all increase with increasing magnetic activity. The meridional wind is less consistent in its behaviour. It is normally equatorward but during magnetic activity it can increase, decrease, or even reverse, although it is consistently equatorward and of increased strength after 02.00 L.T. The initial reversal of the zonal wind is consistent with changes in the wind expected as a result of convective electric fields penetrating to mid-latitudes indicating that these electric fields modify the mid-latitude wind pattern before effects due to auroral heating reach mid-latitudes. The reversal of the zonal wind back to eastward may also be the result of electric field effects. The large variability of the meridional wind, to the extent that it becomes poleward at times, indicates the importance of wind sources equatorward of the observatory.  相似文献   

Announcement     

K. Yagi  S. Akimoto 《Marine Geophysical Researches》1988,9(2):195-195

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Geological and geomorphological characteristics of landslides triggered by the 2004 Mid Niigta prefecture earthquake in Japan   总被引：8，自引：0，他引：8  

Masahiro Chigira  Hiroshi Yagi 《Engineering Geology》2006,82(4):202-221

The 2004 Mid Niigta prefecture earthquake (M_JMA 6.8) triggered more than one thousand landslides in the Miocene to Quaternary sedimentary rocks in Japan. The most common landslides were shallow disrupted landslides on steep slopes, which has been common in many previous disastrous earthquakes in the world. The Mid Niigta prefecture earthquake also triggered more than one hundred deep landslides, providing valuable information on the conditions for their occurrence. A field investigation and the interpretation of aerial photographs taken before and after the earthquake suggest that reactivation of existing landslides and undercutting of slopes are the most important factors for deep landslides to be triggered by earthquakes. In addition, planar sliding surfaces seem to be essential for the generation of catastrophic landslides triggered by this earthquake. Planar bedding–parallel sliding surfaces were formed at the boundary between the overlying permeable sandstone and underlying siltstone or along the bedding planes of alternating beds of sandstone and siltstone. Sliding surfaces along the slope-parallel oxidation front were formed in the area of black mudstone. New landslides (rockslide-avalanches) occurred with the sliding surfaces in a several-cm thick tuff interbedded in siltstone. One rockslide-avalanche occurred on a slope where buckling deformation preceded the earthquake. Gentle valley bottom sediments were mobilized in many locations, probably because they were saturated and partial liquefaction had occurred due to the earthquake shaking.  相似文献   

Slip-weakening distance in dynamic rupture of in-slab normal-faulting earthquakes   总被引：1，自引：0，他引：1  

Takeshi Mikumo  Yuji Yagi 《Geophysical Journal International》2003,155(2):443-455

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Theoretical and experimental evidence for the post-cotunnite phase transition in zirconia at high pressure     

Daisuke Nishio-Hamane  Haruhiko Dekura  Yusuke Seto  Takehiko Yagi 《Physics and Chemistry of Minerals》2015,42(5):385-392

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Raman spectra of methane hydrate up to 86 GPa     

Shin-Ichi Machida  Hisako Hirai  Taro Kawamura  Yoshitaka Yamamoto  Takehiko Yagi 《Physics and Chemistry of Minerals》2007,34(1):31-35

High-pressure Raman studies of methane hydrate were performed using a diamond anvil cell in the pressure range of 0.1–86 GPa at room temperature. Raman spectra of the methane molecules revealed that new softened intramolecular vibration mode of ν ₁ appeared at 17 GPa and that the splitting of vibration mode of ν ₃ occurred at 15 GPa. The appearance of these two modes indicates that an intermolecular attractive interaction increases between the methane molecules and the host water molecules and between the neighboring methane molecules. These interactions might result in the exceptional stability of a high-pressure structure, a filled ice Ih structure (FIIhS) for methane hydrate, up to 40 GPa. At 40 GPa, a clear change in the slope of the Raman shift versus pressure occurred, and above 40 GPa the Raman shift of the vibration modes increased monotonously up to 86 GPa. A previous XRD study showed that the FIIhS transformed into another new high-pressure structure at 40 GPa. The change in the Raman spectra at 40 GPa may be induced by the transition of the structure.  相似文献   

The use of sintered diamond anvils in the MA8 type high-pressure apparatus     

Tadashi Kondo  Hiroshi Sawamoto  Akira Yoneda  Manabu Kato  Akihito Matsumuro  Takehiko Yagi  Takumi Kikegawa 《Pure and Applied Geophysics》1993,141(2-4):601-611

A new multi-anvil type high-presure apparatus has been developed using sintered diamond anvils to generate pressures over 30 GPa and temperatures up to about 2000°C. A maximum sample volume of about 1 mm³ is available in this system. The pressure was confirmed by dissociation of forsterite into Mg-perovskite and periclase. The basic techniques and problems in utilizing sintered diamond in the MA8 type high-pressure apparatus are discussed with an emphasis on the future prospect of incorporating simultancous X-ray diffraction observation.  相似文献   

Synthesis of kosmochlor and phase equilibria in the join CaMgSi2O6-NaCrSi2O6     

Ko Ikeda  Kenzo Yagi 《Contributions to Mineralogy and Petrology》1972,36(1):63-72

Kosmochlor (NaCrSi₂O₆) was synthesized by the flux method from melts along the join Na₂O·2 SiO₂-Na₂O·Cr₂O₃·4 SiO₂ at 1000° C in air, and isolated by dissolving the glassy matrix with hydrofluoric and perchloric acids. The join CaMgSi₂O₆-NaCrSi₂O₆ was studied at 1 atmosphere in air by the quenching technique at temperatures between 900° and 1450° C, using mixtures of kosmochlor and diopside crystals or diopside glass as starting materials. The phases are diopside solid solution, kosmochlor, spinel (Mg-chromite), eskolaite (Cr₂O₃) and glass. The maximum solubility of kosmochlor in diopside is 24 wt percent at 1140° C, while diopside is not soluble at all in kosmochlor, resulting in the existence of a wide range of immiscibility. Petrologic significance of the results is discussed.  相似文献   

Geochemistry of the alkalic dolerites of the nemuro peninsula,Japan     

K. Yagi 《Bulletin of Volcanology》1969,33(4):1101-1117

Many sheets of alkalic dolerites found in the Cretaceous formations in the Nemuro peninsula can be divided into the following two types. Differentiated sheets, more than 100 m in thickness. Gravitational differentiationin situ is distinguished, producing rock types such as picritic dolerite, dolerite, monzonite and syenite. Undifferentiated sheets, less than 30 m in thickness. Differentiationin situ is not observed, and dolerite is the only rock type. Distinguished pillow structures are commonly observed. Petrochemistry of these rocks indicates that K.O contents are high, especially in the middle and later stages, predominating over Na₂O and that MgO content is rather high as compared with iron oxides. These features place the suite in a characteristic position clearly distinguished from the other alkalic rock suites in Japan. Fourteen trace elements were determined spectroscopically and their distribution during the differentiation is discussed. The parent magma of the Nemuro rocks is estimated to be shonkinitic in composition, rather rich in potash. Its possible genesis by the partial melting of the phlogopite-peridotite in the upper mantle under the continent is discussed.  相似文献   

Equilibrium interface segregation in the diopside-forsterite system I: Analytical techniques, thermodynamics, and segregation characteristics     

Takehiko Hiraga  David L. Kohlstedt 《Geochimica et cosmochimica acta》2007,71(5):1266-1280

After syntheses of partially molten diopside-forsterite polycrystalline aggregates doped with various solutes, we analyzed the equilibrium segregation of Ni, Mn, Sr, Al, Yb, Y, Nd, La, and Ti at interfaces between diopside/diopside, diopside/forsterite and, forsterite/forsterite grains based on STEM/EDX (scanning transmission electron microscopy/energy dispersive X-ray spectrometry) to examine the effects of ionic size, valence state, co-segregation, and interface type on interface chemistry. We derive relationships between two quantities describing interface segregation and X-ray intensities acquired both from areas that include an interface and from areas that do not. These segregation quantities are (i) interface excess density and (ii) interface enrichment factor, which rely on Gibbsian thermodynamics and the Langmuir-McLean segregation model, respectively. Interface excess densities, which vary from −0.5 to 10 atoms/nm², indicate that the level of interface excess density depends on solutes and sample assemblage. Interface enrichment factors, which range from almost 1 to 130, reveal that the ionic size of the solutes affects their segregation via production of misfit lattice strain due to the difference between the size of a solute ion and that of the ideal strain-free lattice site. The ionic sizes of Yb and Y are almost identical to the size of the strain-free site; however, their segregation is significant indicating that a difference in valence state between the host elements (i.e., Ca and Mg) and the solutes also drives segregation. In contrast to other solutes, segregation characteristics of Al differ from these simple segregation rules. Segregation quantities do not change with interface type, indicating that the number of sites available for segregants and the driving force for segregation are similar among type of interfaces. We compare the element partitioning between diopside-melt and diopside-interfaces within the same sample assemblages. These two partition coefficients coincide if we approximate the number of segregation sites at interfaces as equivalent to 2 mono-atomic layers. Examination of the energetics in crystal-melt partitioning reveals that the interface segregation energy is essentially equal to the solute solution energy in a crystal.  相似文献