Workshop on Formation of the First Solids in the Solar System—Honoring Klaus Keil for his Distinguished Career in Meteoritics and Cosmochemistry     

G. Jeffrey Taylor  Edward R. D. Scott  Gary R. Huss  Alexander N. Krot  Kazuhide Nagashima 《Meteoritics & planetary science》2012,47(12):1889-1890

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Comparison of heat balance characteristics at five glaciers in the Southern Hemisphere     

Yukari Takeuchi  Renji Naruse  Kazuhide Satow  Nobuyoshi Ishikawa 《Global and Planetary Change》1999,22(1-4)

Ablation characteristics of five glaciers in Patagonia and New Zealand were compared. Investigated glaciers were Tyndall and Moreno in southern Patagonia, Soler and San Rafael in northern Patagonia, and Franz Josef in New Zealand. Micro-meteorological observations were carried out at the glaciers and the heat balance components were estimated. At Franz Josef and Soler glaciers, the sensible heat flux is the largest and the latent heat flux is the second, and they are larger than the net radiation. At San Rafael Glacier, the net radiation is the largest and the latent heat flux is the smallest component, which is similar to Moreno and Tyndall glaciers. Though the latent heat flux is the smallest component at San Rafael Glacier, it is more than twice as large as that at Tyndall Glacier and contributes substantially to ice melting. The ratios of heat balance components were very different among glaciers, but the total heat flux ranged from about 240 to 300 W m⁻² showing little difference among glaciers.  相似文献   

Underwater observations of the giant spoon worm <Emphasis Type="Italic">Ikeda taenioides</Emphasis> (Annelida: Echiura: Ikedidae) in a subtidal soft-bottom environment in northeastern Japan,which survived tsunamis of the 2011 off the Pacific Coast of Tohoku Earthquake     

Ryutaro Goto  Shingo Sakamoto  Jun Hayakawa  Koji Seike 《Journal of Oceanography》2017,73(1):103-113

Tsunamis associated with the 2011 off the Pacific Coast of Tohoku Earthquake seriously disrupted the shallow marine ecosystem along a 2000 km stretch of the Pacific coast of Japan. The effects of the 2011 tsunamis on the soft-bottom benthic community have been relatively well studied in the intertidal zone, whereas tsunami effects on the subtidal benthos remain poorly understood. Here, we investigated populations of the world’s largest spoon worm Ikeda taenioides (Annelida: Echiura: Ikedidae) in subtidal zone of Funakoshi Bay, Tohoku District, northeastern Japan. Subtidal scuba-diving surveys at two sites in the bay showed extremely long proboscises frequently extending from small holes in the sandy seafloor shortly before and soon after the tsunami disturbances. Based on morphological and molecular identification, the proboscises were revealed to be parts of I. taenioides. On 30 November 2011, 265 days after the tsunami event, many large-sized individuals with >1 m long proboscises were observed; these individuals were probably not derived from post-tsunami larval recruitment but more likely survived the tsunami disturbances. This is surprising because other sympatric megabenthos (e.g. spatangoid echinoids and venerid bivalves) and seagrass beds were almost completely destroyed (although they later recovered) by the tsunamis in this bay. The burrows of I. taenioides are known to be very deep (70–90 cm), which may have sheltered them from the impacts of the tsunamis. Our observations suggest that the effects of the 2011 tsunamis on benthos in soft sediments may differ depending on their burrowing depth.  相似文献   

Fractal characteristics of the ULF emissions along a meridian profile, based on the 210 MM stations data     

Anton Varlamov  Natalia Smirnova  Masashi Hayakawa  Kiyohumi Yumoto 《Acta Geophysica》2012,60(3):928-941

Fractal analysis of magnetic records (1 Hz sampling rate) of 5 stations (Guam, Moshiri, Paratunka, Magadan, and Chokurdakh) located along the 210 magnetic meridian (210 MM) has been performed using the Higuchi method. The period of 22 months (October 1992 to July 1994) that embodies the date of the strong Guam earthquake of 8 August1993 has been considered. A comparison of the ULF emissions scaling parameters (spectral exponents β and fractal dimensions D) obtained at different latitudes has been made. Dependence of β and D on the Kp index of geomagnetic activity has been analyzed for each of the 24 local time intervals. It is revealed that D decreases ( β increases) with increasing geomagnetic activity at all stations, but the rates of decrease (increase) are different at different stations and in different time intervals. It is shown that the evening, night and early morning hours are preferable to study magnetospheric effects, whereas the noon hours are the most suitable for the analysis of lithospheric effects. A possibility of using the data of the 210 MM stations as reference materials for the Guam seismically active area is discussed.  相似文献   

Transient Electric Field in the Mesosphere above a Γ-shape Lightning Stroke     

Irina G. Kudintseva  Alexander P. Nickolaenko  Masashi Hayakawa 《Surveys in Geophysics》2010,31(4):427-448

We describe the space–time distribution of the pulsed electric field in the middle atmosphere above a positive Γ-shaped lightning stroke. The channel of such a discharge contains a vertical and a horizontal section. The current wave moves initially vertically and then turns horizontally so that radiation appears from the vertical electric dipole followed by that from the horizontal dipole. Combined with reflection from the perfectly conducting ground, the source provides three subsequent pulses in the atmosphere, with the lag being determined by the finite velocity of the current wave in the Γ-shaped stroke. The pulses are reproduced by reflections from the air-ground and the air-ionosphere interfaces and the waveform resembles the M-component, which is often noted in the negative strokes (e.g. Yashunin et al., J Geophys Res 112:D10109, 2007). The non-stationary fine structure appears in the spatial distribution of electric field, which persists for 2 ms or even more and exceeds the runaway electron threshold. Estimates support the idea of free electron bunching in the mesosphere by the pulsed electric field. Focusing may occur about 10 km away from the point of electron- field interaction; it is delayed by a few ms from the moment of interaction. The data presented might be helpful in realistic modeling of the red sprite formation.  相似文献   

Estimating the impact force generated by granular flow on a rigid obstruction   总被引：12，自引：4，他引：8  

Shuji Moriguchi  Ronaldo I. Borja  Atsushi Yashima  Kazuhide Sawada 《Acta Geotechnica》2009,4(1):57-71

Flowing sediments such as debris and liquefied soils could exert a tremendous amount of force as they impact objects along their paths. The total impact force generally varies with slope angle, velocity at impact, and thickness of the flowing sediment. Estimation of the impact force of flowing sediments against protective measures such as earth retaining structures is an important factor for risk assessment. In this paper, we conduct small-scale laboratory physical modeling of sand flow at different slopes and measure the impact force exerted by this material on a fixed rigid wall. We also conduct numerical simulations in the Eulerian framework using computational fluid dynamics algorithms to analyze and reproduce the laboratory test results. The numerical simulations take into consideration the overtopping of the wall with sand, which influenced the measured impact force–time history responses. In addition, the numerical simulations are shown to capture accurately the change of the impact force with slope angle. Finally, the modeling approach conducted in this study is used to estimate the quasi-static force generated by the sediment as it comes to rest on the wall following impact.  相似文献   

Shaking Maps for Scenario Earthquakes by Applying the Upgraded Version of the Strong Ground Motion Prediction Method ��Recipe��     

Nobuyuki Morikawa  Shigeki Senna  Yuzuru Hayakawa  Hiroyuki Fujiwara 《Pure and Applied Geophysics》2011,168(3-4):645-657

The strong ground motion prediction method ??Recipe?? was published by the Headquarters for Earthquake Research Promotion (HERP) of Japan. HERP has applied this method to prepare shaking maps for scenario earthquakes in specific active faults. Recently, Recipe was updated following its verification by simulations of strong ground motions associated with the Mw?=?6.6 off-shore earthquake west of Fukuoka prefecture in 2005, which occurred in the northwest part of the Kego fault zone located in northern Kyushu, Japan. One of the prominent changes in the upgraded version of Recipe is the inclusion of a procedure to evaluate seismic intensities on the ground surface from waveforms of S-wave velocity of 400?m/s on the engineering bedrock. By applying the upgraded version of Recipe, we have made shaking-maps for earthquakes in the southeast part of the Kego fault zone, which is located directly below the mega-city of Fukuoka. We assume four source models for scenario earthquakes; the locations of the asperities and the hypocenters vary between the models. The results show that in all cases, disastrous seismic intensities can strike a wide area of Fukuoka city. Differences in the distributions of seismic intensities among the four cases can be clearly observed in the area located on the extension of the source fault. Furthermore, we construct a velocity-layer structure model on the engineering bedrock for the central area of Fukuoka city. We assess not only the distribution of seismic intensities but also waveforms on the ground by using an equivalent linear method for the central area of Fukuoka city.  相似文献   

26Al‐26Mg isotope systematics of the first solids in the early solar system     

Noriko T. Kita  Qing‐Zhu Yin  Glenn J. MacPherson  Takayuki Ushikubo  Benjamin Jacobsen  Kazuhide Nagashima  Erika Kurahashi  Alexander N. Krot  Stein B. Jacobsen 《Meteoritics & planetary science》2013,48(8):1383-1400

High‐precision bulk aluminum‐magnesium isotope measurements of calcium‐aluminum‐rich inclusions (CAIs) from CV carbonaceous chondrites in several laboratories define a bulk ²⁶Al‐²⁶Mg isochron with an inferred initial ²⁶Al/²⁷Al ratio of approximately 5.25 × 10^?5, named the canonical ratio. Nonigneous CV CAIs yield well‐defined internal ²⁶Al‐²⁶Mg isochrons consistent with the canonical value. These observations indicate that the canonical ²⁶Al/²⁷Al ratio records initial Al/Mg fractionation by evaporation and condensation in the CV CAI‐forming region. The internal isochrons of igneous CV CAIs show a range of inferred initial ²⁶Al/²⁷Al ratios, (4.2–5.2) × 10^?5, indicating that CAI melting continued for at least 0.2 Ma after formation of their precursors. A similar range of initial ²⁶Al/²⁷Al ratios is also obtained from the internal isochrons of many CAIs (igneous and nonigneous) in other groups of carbonaceous chondrites. Some CAIs and refractory grains (corundum and hibonite) from unmetamorphosed or weakly metamorphosed chondrites, including CVs, are significantly depleted in ²⁶Al. At least some of these refractory objects may have formed prior to injection of ²⁶Al into the protosolar molecular cloud and its subsequent homogenization in the protoplanetary disk. Bulk aluminum and magnesium‐isotope measurements of various types of chondrites plot along the bulk CV CAI isochron, suggesting homogeneous distribution of ²⁶Al and magnesium isotopes in the protoplanetary disk after an epoch of CAI formation. The inferred initial ²⁶Al/²⁷Al ratios of chondrules indicate that most chondrules formed 1–3 Ma after CAIs with the canonical ²⁶Al/²⁷Al ratio.  相似文献   

A study of the morphology of winter sprites in the Hokuriku area of Japan in relation to cloud charge height     

K. Myokei  Y. Matsudo  T. Asano  T. Suzuki  Y. Hobara  K. Michimoto  M. Hayakawa 《Journal of Atmospheric and Solar》2009,71(5):597-602

Continuous observations of sprites in the Hokuriku area of Japan were performed from two optical sites during the three winter periods. The purpose of this observation is to study the major effect in the appearance of sprites and in determining the morphology of sprites (columns or carrots). Detailed analysis is performed based on the estimation of the height of ?10 °C at the time of sprite occurrence. When the height of ?10 °C is lower than 1800 m, the occurrence of sprites is infrequent, and the dominant shape is column. Then when it is increased (1800–3000 m), a new situation takes place, namely the occurrence of sprites is very enhanced and more spectacular shapes like carrots tend to be frequently observed in addition to column sprites. These sprite characteristics are first compared with those of parent lightning in the Hokuriku area and with our latest computer simulations on sprite initiation.  相似文献   

Three-dimensional EM computer simulation on sprite initiation above a horizontal lightning discharge     

T. Asano  T. Suzuki  M. Hayakawa  M.G. Cho 《Journal of Atmospheric and Solar》2009,71(8-9):983-990

The purpose of this paper is to study the three-dimensional (3D) effects of the source current and the electromagnetic (EM) pulse on the distribution of upper atmospheric electric field and ionization created. A new lightning model has been employed; i.e., we have included a horizontal channel in addition to the conventional vertical channel. The effects of the horizontal lightning channel are summarized as follows: (1) the effect of a vertical channel plays a fundamental role in the whole view of sprite initiation; (2) the position of a sprite is shifted from the position of its parent vertical channel in response to the length of a horizontal channel; and (3) we observe very fine structures with local maxima and minima in the “reduced” electric field (the electric field divided by the neutral gas density). These theoretical inferences are discussed and compared with the observational facts so far reported (such as lateral shift of sprites, morphological difference of sprites, etc.).  相似文献