Sweeping-magnetic-twist mechanism for the acceleration of jets in the solar atmosphere     

Kazunari Shibata  Yutaka Uchida 《Solar physics》1986,103(2):299-310

A magnetodynamic mechanism for the acceleration of jets in the solar atmosphere (surges, Brueckner's EUV jets, and so on) is proposed, and a 2.5-dimensional MHD simulation is performed to show how this mechanism operates in the situation of the chromosphere-corona region of the solar atmosphere. It is seen from the result of simulation that together with the release of the magnetic twist, e.g., into a reconnected open flux tube, the mass in the high density twisted loop is driven out into the open flux tube due both to the pinch effect progressing with the packet of the magnetic twist into the open flux tube, and to the j × B force at the front of the packet of the unwinding twist in the off-axis part of the tube. The former, the progressing pinch, is accompanied by an accelerated hot blob, while the latter, the unwinding front of the magnetic twist, drives a cool cylindrical flow, both with velocities of the order of the local Alfvén velocity. One of the characteristic properties of the jet in our model is that the jet, consisting of hot core and cool sheath, has a helical velocity field in it, explaining the thus-far unexplained observed feature.The sudden release of the magnetic twist into an open flux tube is most likely to be due to the reconnection between a twisted loop and the open flux tube. The mass is driven out in the relaxation process of the magnetic twist from the twisted loop to the open flux tube.  相似文献   

BIOCHEMICAL GENETIC STUDIES ON CUTYLEFISH SEPIELLA MAINDRONI （CEPHALOPODA： SEPIIDAE）——ACTIVE LOCI SCREENING OF ISOZYME     

郑小东 YutakaNatsukari王如才  王昭萍李云 《中国海洋湖沼学报》2001,19(4):345-349

Screening of 46 putative enzyme-coding loci and 4 different kinds of tissues of Sepiella maindroni de Rochebrone, 1884 for enzymatic activities using starch gel electrophoretic technique proved that the 21 enzymes such as AAT, AK, ALP, AP, CK, DIA, ES, FBP, G3PDH, GPI, GRS,IDH, LDH, MDH, MEP, MPI, NP, PGDH, PGM, SOD and XO* , were active to Sepiella maindroni after being stained. The tissue exhibiting stable and clear bands was also determined. Among tissues tested, mantle muscle tissue was the best for electrophoretic survey of isozymes. Buccal bulb muscle, eye and liver were fairly good for some special enzymes, such as DIA, ES, MPI, NT, etc.  相似文献   

YAMATO METEORITES COLLECTED IN ANTARCTICA IN 1969     

Takesi Nagata 《Meteoritics & planetary science》1976,11(2):181-184

The meteoritic community has been tantalized by reports of extensive meteorite finds in Antarctica by members of the Japanese Antarctic Research Expedition. The National Institute of Polar Research has published this introduction and review of the Yamato meteorites collected in Antarctica in 1969. This welcome review reveals that nine meteorite fragments of meteoritic material were found in the region of the Yamato Mountains. Four pieces greater than 60 g in weight have been identified as an enstatite chondrite, a hypersthene achondrite, a type III carbonaceous chondrite and a bronzite chondrite. In 1973 eleven additional suspected meteorites were recovered. Preliminary results show that three bronzite chondrites and one achondrite are among the new finds. In 1974 over 600 pieces of meteorite-like rock have been collected. The volume contains five articles on the original 1969 material. These include a general discussion on their discovery including photographs of the individuals, and notes on the chemical, mineralogical and petrological characteristics of the four large samples. Two articles deal with detailed mineralogic and magnetic properties of these specimens. Information on these interesting finds is welcome. Information on the 1969 and 1974 material is anxiously awaited.  相似文献   

地表刚性对地震液化作用的影响          下载免费PDF全文

Yukitake SHIOI  Yutaka HASHIZUME  Hisasi FUKADA 《地震工程学报》2005,27(3):205-211

一种新的假说阐述了在大地震中饱和沙土的液化现象。这是建立在多反射理论和FEM动力反应计算的基础上的。计算中应用了在1994年三陆外海M7.5地震时对八户港土层的假设,其结果与观测到的地震现象十分符合。这种方法也被应用于其他曾经发生液化的地区并被证实是在液化机理可接受限度内。富井地震(1948年6月,M=7.1)发生在福井盆地中央,深度为15 km,引起了大范围的破坏,伤亡人数达到5 300人。这次地震在各处引起大面积的液化,导致大范围的稻田被砂石所覆盖。但是,尽管加速度很大,盆地的几部分没有被液化。应用这种假说,我们分析了在相同情况下地表层的差异。结果发现液化的产生取决于地表层刚性引起的应变大小,假设与实际情况一致。  相似文献   

Geochemistry of adakitic quartz diorite in the Yamizo Mountains, central Japan: Implications for Early Cretaceous adakitic magmatism in the inner zone of southwest Japan     

Yutaka  Takahashi  Shin-Ichi  Kagashima  Masumi U.  Mikoshiba 《Island Arc》2005,14(2):150-164

Abstract   Small-volume plutons of Early to Late Cretaceous ages are widely distributed in the Yamizo Mountains, central Japan. These plutons consist predominantly of granitoids, classified into hornblende gabbro, quartz diorite, hornblende–biotite granodiorite and coarse-grained biotite granite. The quartz diorite (52–64 wt% of SiO₂) is characterized by a high Sr content (606–769 p.p.m.) associated with a low Y (13–27 p.p.m.) and heavy rare earth element content (Yb content of 1.19–2.13 p.p.m.). On the Sr/Y versus Y diagram, this rock type mainly plots in the adakite and Archean high-Al tonalite, trondhjemite and granodiorite (TTG) field. Together with its initial Sr isotopic ratios, which range from 0.7038 to 0.7046, these data suggest that quartz diorite originated as slab melts. However, geochemical calculations assuming either eclogite or garnet amphibolite as the source material do not support this suggestion. Instead, the chemical compositions of quartz diorite are better explained by the fractional crystallization of hornblende, plagioclase and biotite from a primitive, basaltic melt in a magma chamber. In this case, the formation of the associated hornblende gabbro can also be explained by the accumulation of hornblende and plagioclase. Adakitic rocks of Early Cretaceous ages have also been reported in the Tamba Belt of the inner zone of southwest Japan, located ca 500 km west of the Yamizo Mountains. These rocks can be correlated to the adakitic rocks in the Yamizo Mountains based on the geology, petrography, geochemistry and radiometric ages. Therefore, we propose the possibility that the Early Cretaceous adakitic rocks in the inner zone of southwest Japan were produced by fractional crystallization from basaltic arc magmas generated by a partial melting of metasomatized wedge mantle peridotite.  相似文献   

Cenozoic stratigraphy and sedimentation history of the northern Philippine Sea based on multichannel seismic reflection data     

Yu  Higuchi  Yutaka  Yanagimoto  Kazuyoshi  Hoshi  Sadao  Unou  Fumio  Akiba  Kunishige  Tonoike  Keita  Koda 《Island Arc》2007,16(3):374-393

Abstract To clarify the regional distribution and characteristics of the sedimentary deposits in the northern part of the Philippine Sea, multichannel seismic reflection surveys of 26 864 km in total length were performed. The seismic reflection data were interpreted and correlated with available Deep Sea Drilling Project/Ocean Drilling Program (DSDP/ODP) data and a general stratigraphic framework of the area was established. The sedimentary deposits in this area were divided into five layers; Units I, II, III, IV and V in ascending order. Their approximate geological ages are the Early Eocene, Middle to Late Eocene, Oligocene, Miocene and Pliocene‐Pleistocene, respectively. Seismic records were classified into three seismic facies, Facies A, B and C, on the basis of their characteristics. They were judged to represent pelagic and hemipelagic sediments of non‐volcanic origin, fine pyroclastic sediments and coarse pyroclastic or volcanic sediments, respectively, by comparing them with lithological data in the DSDP/ODP holes. From the thickness and facies distributions of these sediments, a sedimentary history in the area was reconstructed as follows. The oldest sediments in the study area, Unit I, interfinger with some parts of the Daito Ridge (acoustic basement) in the Minami Daito Basin. The geological age of the unit is estimated by microfossils in the sediment and supports the idea that this part of the Daito Ridge is composed of the Early Eocene oceanic basalt. Later, a fair amount of sediments were deposited in the Minami Daito Basin in the Middle to Late Eocene age. A large volume of volcanic materials was supplied from the Paleo‐Kyushu‐Palau Ridge in the Kita Daito Basin in the Eocene and Oligocene ages. The eastern part of the Shikoku and Parece Vela basins is characterized by volcanic sediments supplied from the Nishi Shichito and West Mariana Ridges in the Miocene age. However, pelagic and hemipelagic sediments prevail in the northern part of the Shikoku Basin in the Miocene or later. In short, the area of principal sedimentation has generally shifted from west to east through geological time, reflecting the evolution of the island arc systems with the same trend in the northern Philippine Sea.  相似文献   

Chemical evidence for the origin of the cold water belt along the northeastern coast of Hokkaido     

Kenshi Kuma  Ryohei Sasayama  Nanako Hioki  Yuichiroh Morita  Yutaka Isoda  Tohru Hirawake  Keiri Imai  Takafumi Aramaki  Tomohiro Nakamura  Jun Nishioka  Naoto Ebuchi 《Journal of Oceanography》2014,70(4):377-387

In the southwestern Okhotsk Sea, the cold water belt (CWB) is frequently observed on satellite images offshore of the Soya Warm Current flowing along the northeastern coast of Hokkaido, Japan, during summertime. It has been speculated that the CWB is upwelling cold water that originates from either subsurface water of the Japan Sea off Sakhalin or bottom water of the Okhotsk Sea. Hydrographic and chemical observations (nutrients, humic-type fluorescence intensity, and iron) were conducted in the northern Japan Sea and southwestern Okhotsk Sea in early summer 2011 to clarify the origin of the CWB. Temperature–salinity relationships, vertical distributions of chemical components, profiles of chemical components against density, and the (NO₃ + NO₂)/PO₄ relationship confirm that water in the CWB predominantly originates from Japan Sea subsurface water.  相似文献   

Linear stability analysis for the differentially heated rotating annulus     

Gregory M. Lewis  Wayne Nagata 《地球物理与天体物理流体动力学》2013,107(2):129-152

We use linear stability analysis to approximate the axisymmetric to nonaxisymmetric transition in the differentially heated rotating annulus. We study an accurate mathematical model that uses the Navier–Stokes equations in the Boussinesq approximation. The steady axisymmetric solution satisfies a two-dimensional partial differential boundary value problem. It is not possible to compute the solution analytically, and thus, numerical methods are used. The eigenvalues are also given by a two-dimensional partial differential problem, and are approximated using the matrix eigenvalue problem that results from discretizing the linear part of the appropriate equations.

A comparison is made with experimental results. It is shown that the predictions using linear stability analysis accurately reproduce many of the experimental observations. Of particular interest is that the analysis predicts cusping of the axisymmetric to nonaxisymmetric transition curve at wave number transitions, and the wave number maximum along the lower part of the axisymmetric to nonaxisymmetric transition curve is accurately determined. The correspondence between theoretical and experimental results validates the numerical approximations as well as the application of linear stability analysis.

A linear stability analysis is also performed with the effects of centrifugal buoyancy neglected. Along the lower part of the transition curve, the results are significantly qualitatively and quantitatively different than when the centrifugal effects are considered. In particular, the results indicate that the centrifugal buoyancy is the cause of the observation of a wave number maximum along the transition curve, and is the cause of a change in concavity of the transition curve.  相似文献   

Shear flow instability of rotating hydromagnetic fluids     

M. Nagata 《地球物理与天体物理流体动力学》2013,107(1-4):173-184

Abstract

The effect of an axial magnetic field on the linear stability of shear flows in rotating systems is examined by extending Busse's analysis of the nonmagnetic case to fluids of high magnetic diffusivity in the presence of a magnetic field. The shear is caused by differential rotation which creates slight deviations from a state of rigid rotation, corresponding to a small Rossby number. It is found that the Rossby number for the onset of instability is larger when a magnetic field is present than when it is absent.  相似文献   

Nutrient status of Otsuchi Bay (northeastern Japan) following the 2011 off the Pacific coast of Tohoku Earthquake     

Hideki Fukuda  Ryosuke Katayama  Yanhui Yang  Hiroyuki Takasu  Yuichiro Nishibe  Atsushi Tsuda  Toshi Nagata 《Journal of Oceanography》2016,72(1):39-52

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