Spatial variability of chemical tracers in surface snow along the traverse route from the coast to 1000 km inland at east Dronning Maud Land, Antarctica   总被引：1，自引：0，他引：1  

Toshitaka Suzuki  Yoshinori Iizuka  Teruo Furukawa  Kenichi Matsuoka  Kokichi Kamiyama  Okitsugu Watanabe 《极地研究(英文版)》2003,14(1)

1　IntroductionAntarcticicesheetisaburialgroundforatmosphericdeposition .Sincethereiscon tinuousinteractionbetweentheicesheetandtheatmosphere,variousatmosphericsub stancesareinjectedtotheicesheetsequentiallyintimeandspace.Therefore,verticalanalysesoftheicesheetprovideuswithinformationaboutpastclimaticchange (Delmas1 992 ;LegrandandMayewski 1 997)andhorizontalanalysesoftheicesheetprovideuswithknowledgeregardinglong rangetransportofairbornematerials (Kamiyamaetal.1 989;KreutzandMayewski 1 999)…  相似文献   

Co-accretion of the Earth-Moon system after the giant impact: reduction of the total angular momentum by lunar impact ejecta     

Ryuji Morishima  Sei-ichiro Watanabe 《Icarus》2004,168(1):60-79

Though the Moon is considered to have been formed by the so-called giant impact, the mass of the Earth immediately after the impact is still controversial. If the Moon was formed during the Earth's accretion, a subsequent accretion of residual heliocentric planetesimals onto the protoearth and the protomoon must have occurred. In this co-accretion stage, a significant amount of lunar-impact-ejecta would be ejected to circumterrestrial orbits, since the mean impact velocity of the planetesimals with the protomoon is much larger than the escape velocity of the protomoon. Orbital calculations of test particles ejected from the protomoon, whose semimajor axis is smaller than that of the present Moon, reveal that most of the particles escaping from the protomoon also escape from the Hill sphere of the protoearth and reduce the planetocentric angular momentum of the primordial Earth-Moon system. Using the results of the ejecta simulations, we investigate the evolution of the mass ratio and the total angular momentum (Earth's spin angular momentum + Moon's orbital angular momentum) of the Earth-Moon system during the co-accretion. We find that the mass of the protomoon is almost constant or rather decreases and the total angular momentum decreases significantly, if the random velocity of planetesimals is as large as the escape velocity of the protoearth. On the other hand, if the random velocity is the half of the escape velocity of the protoearth, the mass ratio is kept to be almost as large as the present value and the decrease of the total angular momentum is not so significant. Comparing with the results of giant impact simulations, we find that the mass of the protoearth immediately after the Moon-forming impact was 0.7-0.8 times the present value if the impactor-to-target mass ratio was 3:7, whereas the giant impact occurred almost in the end of the Earth's accretion if the impactor-to-target mass ratio was 1:9.  相似文献   

Hydrothermal synthesis of pumpellyite–okhotskite series minerals     

M. Akasaka  Y. Suzuki  H. Watanabe 《Mineralogy and Petrology》2003,77(1-2):25-37

Summary ?Hydrothermal experiments to synthesize pumpellyite group minerals of the pumpellyite–okhotskite series and to investigate their stability have been carried out at 200, 300 and 400 MPa P _fluid and 250–500 °C by using cold-seal pressure vessels and solid buffers of MnO₂–Mn₂O₃, Cu₂O–CuO and Cu₂O–Cu buffer assemblages. Okhotskite and pumpellyite rich in the okhotskite component crystallized from an oxide mixture starting material of Ca₄MgMn³⁺ ₃Al₂Si₆O_24.5-oxide+excess H₂O at P _fluid of 200, 300 and 400 MPa and temperatures of 300 and 400 °C. However, a single phase of okhotskite was not produced, and associated piemontite, hausmannite, wollastonite, clinopyroxene, corundum, braunite–neltnerite solid solution and alleghanyite also formed. Mn-pumpellyite of the okhotskite–pumpellyite join occurs as aggregates of needle crystals, rounded grains or flaky crystals. Chemical compositions are variable and range from pumpellyite-(Mn²⁺) to okhotskite: 31–36 SiO₂, 13–21 Al₂O₃, 12–25 total Mn₂O₃, 0.6–4 MgO and 20–24 wt.% CaO. Reconnaissance experiments using a starting material of synthetic Ca₂Mn³⁺Al₂Si₃O₁₂(OH)-piemontite at 300 MPa and temperatures of 250, 300, 400 and 500 °C indicate that Mn-rich pumpellyite can crystallize from piemontite at lower temperatures than the stability field of piemontite. The Mn-rich pumpellyite was accompanied by garnet, wollastonite and alleghanyite. The chemical compositions of the Mn-pumpellyites are 32–36 SiO₂, 18–27 Al₂O₃, 8–18 total Mn₂O₃ and 20–23 wt.% CaO. This study shows that the stability fields of piemontite, piemontite+Mn-pumpellyite, and Mn-pumpellyite range in this order with decreasing temperature under high fO₂ conditions. The maximum stability temperature of Mn-rich pumpellyite lies between 400 and 500 °C at 200–400 MPa in high fO₂ conditions. Received March 3, 2000; revised version accepted December 28, 2001  相似文献   

The EUV Imaging Spectrometer for Hinode   总被引：1，自引：0，他引：1  

J. L. Culhane  L. K. Harra  A. M. James  K. Al-Janabi  L. J. Bradley  R. A. Chaudry  K. Rees  J. A. Tandy  P. Thomas  M. C. R. Whillock  B. Winter  G. A. Doschek  C. M. Korendyke  C. M. Brown  S. Myers  J. Mariska  J. Seely  J. Lang  B. J. Kent  B. M. Shaughnessy  P. R. Young  G. M. Simnett  C. M. Castelli  S. Mahmoud  H. Mapson-Menard  B. J. Probyn  R. J. Thomas  J. Davila  K. Dere  D. Windt  J. Shea  R. Hagood  R. Moye  H. Hara  T. Watanabe  K. Matsuzaki  T. Kosugi  V. Hansteen  Ø. Wikstol 《Solar physics》2007,243(1):19-61

The EUV Imaging Spectrometer (EIS) on Hinode will observe solar corona and upper transition region emission lines in the wavelength ranges 170?–?210 Å and 250?–?290 Å. The line centroid positions and profile widths will allow plasma velocities and turbulent or non-thermal line broadenings to be measured. We will derive local plasma temperatures and densities from the line intensities. The spectra will allow accurate determination of differential emission measure and element abundances within a variety of corona and transition region structures. These powerful spectroscopic diagnostics will allow identification and characterization of magnetic reconnection and wave propagation processes in the upper solar atmosphere. We will also directly study the detailed evolution and heating of coronal loops. The EIS instrument incorporates a unique two element, normal incidence design. The optics are coated with optimized multilayer coatings. We have selected highly efficient, backside-illuminated, thinned CCDs. These design features result in an instrument that has significantly greater effective area than previous orbiting EUV spectrographs with typical active region 2?–?5 s exposure times in the brightest lines. EIS can scan a field of 6×8.5 arc?min with spatial and velocity scales of 1 arc?sec and 25 km?s^?1 per pixel. The instrument design, its absolute calibration, and performance are described in detail in this paper. EIS will be used along with the Solar Optical Telescope (SOT) and the X-ray Telescope (XRT) for a wide range of studies of the solar atmosphere.  相似文献   

Gold Mineralization at the Agawa Prospect in Yamaguchi Prefecture,Southwestern Japan          下载免费PDF全文

Ryuya Sato  Osao Sawai  Yasushi Watanabe 《Resource Geology》2016,66(2):199-212

Agawa gold prospect, located in Yamaguchi Prefecture, southwestern Japan, is a small prospect, where placer gold has been explored and mined since the 17th century. We investigated the prospect to clarify the genesis of the deposit based on the geology, hydrothermal alteration, geochronology, and ore mineralogy. The main mineralized zone of the prospect has a horizontal and vertical extensions of 500 m and 100 m, respectively, and a width of less than 100 m. Gold mineralization in the prospect occurs as dissemination and stockwork veinlets in the intensely sericitized rocks at the apical part of the Agawa dioritic porphyry intrusion at 86.5–88.5 Ma. Mineralization is typified by at least three stages – an early stage characterized by the occurrence of pyrrhotite and native gold; a middle stage by chalcopyrite; and a late stage by pyrite–bornite. Mineral assemblage and fluid inclusion microthermometry estimation suggest a trend of decreasing temperatures from 400°C to 160°C at a constant sulfur fugacity. The mineralizing fluids formed by the mixing of a hypogene fluid of possibly magmatic origin with an external lower‐temperature and lower‐salinity fluid. The mixing process decreased the temperature and salinity of the fluid, resulting in the precipitation of sulfides, native gold and Bi–Te alloys and sulfosalts. The magnetite‐series signature of the Agawa porphyry and related molybdenite‐bearing mineralization indicate that the plutonism of the San‐in granitoids belt extends to the westernmost end of the Honshu Island. The compiled geochronology and distribution of the metallic deposits in the southwestern Japan arc show that transition from ilmenite‐series to magnetite‐series plutonism started earlier in the west, and shifted eastwards with time during the period from Late Cretaceous to Paleogene.  相似文献   

Plasmaspheric hiss observed in the topside ionosphere at mid- and low-latitudes     

T. Ondoh  Y. Nakamura  S. Watanabe  K. Aikyo  T. Murakami 《Planetary and Space Science》1983,31(4):411-422

Latitudinal characteristics of ELF hiss in mid- and low-latitudes have been statistically studied by using ELF/VLF electric field spectra (50 Hz-30 kHz) from ISIS-1 and -2 received at Kashima station, Japan from 1973 to 1977. Most ISIS ELF/VLF data observed in mid- and low-latitude include ELF hiss at frequencies below a few kHz. The ELF hiss has the strongest intensity among VLF phenomena observed by the ISIS electric dipole antenna in mid- and low-latitudes, but the ELF hiss has no rising structure like the chorus in the detailed frequency-time spectrum. The ELF hiss is classified into the steady ELF hiss whose upper frequency limit is approximately constant with latitude and the ELF hiss whose upper frequency limit increases with latitude. These two types of ELF hiss occur often in medium or quiet geomagnetic activities. Sometimes there occurs a partial or complete lack of ELF hiss along an ISIS pass.Spectral shape and bandwidth of ELF hiss in the topside ionosphere are very similar to those of plasmaspheric hiss and of inner zone hiss. The occurrence rate of steady ELF hiss is about 0.3 near the geomagnetic equator and decreases rapidly with latitude around L = 3. Hence it seems likely that ELF hiss is generated by cyclotron resonant instability with electrons of several tens of keV in the equatorial outer plasmasphere beyond L = 3.Thirty-seven per cent of ELF hiss events received at Kashima station occurred during storm times and 63% of them occurred in non-storm or quiet periods. Sixty-seven per cent of 82 ELF hiss events during storm times were observed in the recovery phase of geomagnetic storms. This agrees with the previous satellite observations of ELF hiss by search coil magnetometers. The electric field of ELF hiss becomes very weak every 10 s, which is the satellite spin period, in mid- and low-latitudes, but not near the geomagnetic equator. Ray tracing results suggest that waves of ELF hiss generated in the equatorial outer plasmasphere propagate down in the electrostatic whistler mode towards the equatorial ionosphere, bouncing between the LHR reflection points in both the plasmaspheric hemispheres.  相似文献   

Seismic experiments on Showa-Shinzan lava dome using firework shots     

Hiroki Miyamachi  Hidefumi Watanabe  Takeo Moriya  Hiromu Okada 《Pure and Applied Geophysics》1987,125(6):1025-1037

Seismic experiments were conducted on Showa-Shinzan, a parasitic lava dome of volcano Usu, Hokkaido, which was formed during 1943–1945 activity. Since we found that firework shots fired on the ground can effectively produce seismic waves, we placed many seismometers on and around the dome during the summer festivals in 1984 and 1985. The internal structure had been previously studied using a prospecting technique employing dynamite blasts in 1954. The measured interval velocity across the dome in 1984 ranges 1.8–2.2 km/s drastically low compared to the results (3.0–4.0 km/s) in 1954; in addition, the velocity is 0.3–0.5 km/s higher than that in the surrounding area. The variation of the observed first arrival amplitudes can be explained by geometrical spreading in the high velocity lava dome. These observations show a marked change in the internal physical state of the dome corresponding to a drop in the measured highest temperature at fumaroles on the dome from 800°C in 1947 to 310°C in 1986.  相似文献   

CCD surface photometry of an outburst of P/Schwassmann-Wachmann 1 comet     

Tsuko Nakamura  Jun-Ichi Watanabe  Hajime Kawakami 《Earth, Moon, and Planets》1991,52(1):15-25

We have observed an outburst of P/Schwassmann-Wachmann 1 (SW1) on 25–26 July 1987 using a CCD imager with R-band filter. The total brightness increased from 15.5 mg (25d) to 14.4 mag (26d) during tabout 24 hrs. The southward elongated coma of 25 was detected. The radial surface brightness (B) profiles are plotted against apparent distance p from the nucleus. The logarithmic derivative k = d ln B/d ln p for the inner coma is found to have steepened from k = –1.40 (25d) to k = –1.69 (26d), whereas that for the outer coma showed no appreciable change (k = –1.19 ~ –1.22). The ellipticity of the isophotal contour of the inner coma increased about 15% fro 25d to 6d. It is concluded that the scale of this outburst was smaller than the typical ones whose magnitude change is 5–8 mag. From recent findings on the outburst natur eof SW1 including ours, a working model of the nuclues is proposed.  相似文献   

The Bragg Crystal Spectrometer for SOLAR-A     

J. L. Culhane  E. Hiei  G. A. Doschek  A. M. Cruise  Y. Ogawara  Y. Uchida  R. D. Bentley  C. M. Brown  J. Lang  T. Watanabe  J. A. Bowles  R. D. Deslattes  U. Feldman  A. Fludra  P. Guttridge  A. Henins  J. Lapington  J. Magraw  J. T. Mariska  J. Payne  K. J. H. Phillips  P. Sheather  K. Slater  K. Tanaka  E. Towndrow  M. W. Trow  A. Yamaguchi 《Solar physics》1991,136(1):89-104

The Bragg Crystal Spectrometer (BCS) is one of the instruments which makes up the scientific payload of the SOLAR-A mission. The spectrometer employs four bent germanium crystals, views the whole Sun and observes the resonance line complexes of H-like Fexxvi and He-like Fexxv, Caxix, and Sxv in four narrow wavelength ranges with a resolving power (/) of between 3000 and 6000. The spectrometer has approaching ten times better sensitivity than that of previous instruments thus permitting a time resolution of better than 1 s to be achieved. The principal aim is the measurement of the properties of the 10 to 50 million K plasma created in solar flares with special emphasis on the heating and dynamics of the plasma during the impulsive phase. This paper summarizes the scientific objectives of the BCS and describes the design, characteristics, and performance of the spectrometers.After the launch the name of SOLAR-A has been changed to YOHKOH.Tragically Professor K. Tanaka died on January 2, 1990.  相似文献   

Solar wind velocity and normalized scintillation index from single-station IPS observations   总被引：2，自引：0，他引：2  

P. K. Manoharan  S. Ananthakrishnan  M. Dryer  T. R. Detman  H. Leinbach  M. Kojima  T. Watanabe  J. Kahn 《Solar physics》1995,156(2):377-393

The recently refurbished Ooty Radio Telescope in southern India was used in a two-month campaign of interplanetary scintillation (IPS) observations in collaboration with the Cambridge IPS array in England during April–May 1992. The unique feature of this campaign was that, for the first time, scintillation enhancements were predicted in real time by observing solar events on 7–8 May, 1992 and then detected at both Ooty and Cambridge. Also, for the first time, high spatial resolution ( 100 sources sr^–1) solar wind all-sky velocity maps were obtained at Ooty. Good consistency is found between the IPS observations from both observatories andin-situ shocks detected at Earth by IMP-8.Yohkoh soft X-ray images were used to infer the generation of a coronal mass ejection on 7 May, 1992.  相似文献