Progress report on the determination of seismic moment tensor from long-period surface waves     

Keiiti Aki 《Tectonophysics》1982,84(1):1-2

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Acknowledgement     

Keiiti Aki  Renata Dmowska 《Pure and Applied Geophysics》1987,125(6):1119-1120

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THE NOMENCLATURE OF POLYMICT BASALTIC ACHONDRITES     

Jeremy S. Delaney  H. Takeda  M. Prinz  C.E. Nehru  G.E. Harlow 《Meteoritics & planetary science》1983,18(2):103-111

The subgroups within the basaltic achondrite suite are defined using the structural criterion of Wahl (1952). The ‘monomict’ meteorites are samples of a single lithology while the polymict meteorites are those containing two or more lithologies. The ‘monomict’ subgroups eucrites, cumulate eucrites and diogenites are subdivided into both brecciated and unbrecciated meteorites. The polymict achondrites sample a petrological-compositional continuum that contains both mafic and ultramafic rock types and may be subdivided into several groups. Two groups of polymict basaltic achondrites, the polymict eucrites and howardites are separated using an arbitrarily defined criterion. The recommended criterion is based on the amount of magnesian ortho-pyroxenite (diogenite) component in the meteorite. Howardites contain more than 10% and polymict eucrites contain less than 10%. The criteria proposed (perhaps with minor variations), appear to reconcile the ambiguities caused by the polymict eucrites. These meteorites, using earlier structural criteria, are howardites, but using mineralogical-chemical criteria are eucrites. As a subgroup of the polymict achondrites, their relationship with the howardites is clear, and the preservation of the term ‘eucrite’ in their name highlights their modal affinity to the monomict eucrites.  相似文献   

Eccentricities of Planets in Binary Systems     

Genya Takeda  Frederic A. Rasio 《Astrophysics and Space Science》2006,304(1-4):239-242

The most puzzling property of the extrasolar planets discovered by recent radial velocity surveys is their high orbital eccentricities, which are very difficult to explain within our current theoretical paradigm for planet formation. Current data reveal that at least 25% of these planets, including some with particularly high eccentricities, are orbiting a component of a binary star system. The presence of a distant companion can cause significant secular perturbations in the orbit of a planet. At high relative inclinations, large-amplitude, periodic eccentricity perturbations can occur. These are known as “Kozai cycles” and their amplitude is purely dependent on the relative orbital inclination. Assuming that every planet host star also has a (possibly unseen, e.g., substellar) distant companion, with reasonable distributions of orbital parameters and masses, we determine the resulting eccentricity distribution of planets and compare it to observations? We find that perturbations from a binary companion always appear to produce an excess of planets with both very high (?0.6) and very low (e ? 0.1) eccentricities. The paucity of near-circular orbits in the observed sample implies that at least one additional mechanism must be increasing eccentricities. On the other hand, the overproduction of very high eccentricities observed in our models could be combined with plausible circularization mechanisms (e.g., friction from residual gas) to create more planets with intermediate eccentricities (e? 0.1–0.6).  相似文献   

Characteristics of the Re-Calculated <Emphasis Type="Italic">Yohkoh</Emphasis>/SXT Temperature Response     

A. Takeda 《Solar physics》2011,273(1):295-306

The temperature response functions of the Yohkoh/SXT are re-calculated based on the most recent elemental abundances and ionization balance available in the CHIANTI atomic database version 6.0.1. The new standard responses are calculated for three types of abundance; i.e., ‘coronal’, ‘hybrid’, and ‘photospheric’ abundances included in the CHIANTI database, and are available in SolarSoft since 2010. Comparison plots of the new and old response functions and filter ratios are available at the Yohkoh Legacy data Archive (). The three new responses generally peak at higher temperatures (at ≈ 10 MK) than the former standard response (at ≈ 5.6 MK) based on Mewe’s spectral model. The new responses with coronal and hybrid abundances have higher peak counts by a factor of 3 and 2, respectively, than those with the photospheric abundances and the former response based on Mewe’s model. The correction of the filter ratios depends on the type of filter and the range of the ratios to be used. In the significant cases, the new filter ratio produces 20 to 30% higher temperatures than the previous calibration. The choice of elemental abundance has a strong influence on the derived temperatures and emission measures, and often produces a variation significantly larger than the statistical and systematic errors considered so far.  相似文献   

Detection of Gravitational Redshift on the Solar Disk by Using Iodine-Cell Technique     

Y. Takeda  S. Ueno 《Solar physics》2012,281(2):551-575

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Dissolved iron and zinc in Sagami Bay and the Izu-Ogasawara Trench     

Hajime Obata  Jun Nishioka  Taejin Kim  Kazuhiro Norisuye  Shigenobu Takeda  Yohei Wakuta  Toshitaka Gamo 《Journal of Oceanography》2017,73(3):333-344

Using a clean seawater sampling system for trace metals onboard the R. V. Shinsei-Maru, newly launched in 2013, we investigated the vertical distributions of dissolved iron and zinc in Sagami Bay and the Izu-Ogasawara Trench. We applied appropriate clean sampling and filtering processes for trace metals, so that uncontaminated seawater samples were successfully collected. The distribution of zinc in the trench area was similar to that of silicate and the same as that previously reported in the subtropical North Pacific. There were spatial variations in the iron (Fe) distribution in the trench areas. We used previously reported information about biogeochemical cycling in the trench area, and found that Fe has a residence time of 29 years in the water column. The short residence time of Fe (29 years) corresponds to the vertical variations of dissolved Fe in the water column.  相似文献   

Gamma-Ray Line Observations of the 2000 July 14 Flare and SEP Impact on the Earth     

Share  G.H.  Murphy  R.J.  Tylka  A.J.  Schwartz  R.A.  Yoshimori  M.  Suga  K.  Nakayama  S.  Takeda  H. 《Solar physics》2001,204(1-2):41-53

The HXS and GRS detectors on Yohkoh observed the 14 July 2000, X5.7 flare, beginning at ∼ 10:20 UT, ∼ 4 min before the peak in soft X-rays. The hard X-rays and γ-rays peaked ∼ 3 min later at ∼ 10:27 UT. Solar γ-ray emission lasted until ∼ 10:40 UT. Impact of high-energy ions at the Sun is revealed by the γ-ray lines from neutron capture, annihilation radiation and de-excitation that are visible above the bremsstrahlung continuum. From measurement of these lines we find that the flare-averaged spectrum of accelerated protons is consistent with a power law ge10 MeV with index 3.14±0.15 and flux 1.1×10³² protons MeV⁻¹ at 10 MeV. We estimate that there were ∼1.5×10³⁰ erg in accelerated ions if the power law extended without a break down to 1 MeV; this is about 1% of the energy in electrons > 20 keV from measurements of the hard X-rays. We find no evidence for spectral hardening in the hard X-rays that has been suggested as a predictor for the occurrence of solar energetic particle (SEP) events. This was the third largest proton event above 10 MeV since 1976. The GRS and HXS also observed γ-ray lines and continuum produced by the impact of SEP on the Earth's atmosphere beginning about 13 UT on 14 July. These measurements show that the SEP spectrum softened considerably over the next 24 hours. We compare these measurements with proton measurements in space.  相似文献   

Grain size of the surface regolith of asteroid 4 Vesta estimated from its reflectance spectrum in comparison with HED meteorites     

Takahiro Hiroi  Carl M. Pieters  Hiroshi Takeda 《Meteoritics & planetary science》1994,29(3):394-396

Abstract— The grain-size distribution of the regolith of asteroid 4 Vesta has been estimated by comparing its reflectance spectra (0.3–2.6 μm) with those of HED meteorites. The finest grain-size separate (<25 μm) of a particular howardite has a reflectance spectrum most similar to Vesta's. In order to better simulate Vesta's surface mineralogy, reflectance spectra of those finest HED meteorite powders were linearly combined, and Vesta's spectrum was scaled for the best fit between them. Both the albedo and the shape of reflectance spectrum of Vesta were well reproduced by regional mixtures of the finest (<25 μm) powders of HED meteorites. The result suggests the heterogeneity of Vesta's surface and provides an estimate of the visible reflectance of Vesta that is close to its IRAS albedo. Thus, this suggests that fine grains can be generated and retained by relatively small bodies (Vesta is approximately 500 km in diameter).  相似文献   

Distribution of nitrate over sea-salt and soil derived particles — Implications from a field study   总被引：1，自引：0，他引：1  

Tuomo A. Pakkanen  Veli-Matti Kerminen  Risto E. Hillamo  Minna Màkinen  Timo Màkelà  Aki Virkkula 《Journal of Atmospheric Chemistry》1996,24(2):189-205

A method for determining the distribution of supermicrometer nitrate between size-segregated sea-salt and soil derived particles is presented. The analysis is based on field data from six measurements at a coastal site in southern Finland, and on a theoretical treatment taking into account the transfer of gaseous species onto particle surfaces and their subsequent reaction. Significant amounts of nitrate were found in both the particle types, with the fraction of nitrate associated with soil particles varying from 20–50% in the 1–2 m size to near 90% in particles larger than 10 m. Overall, the nitrate accumulation followed closely the relative abundances of these two particle types. Two overlapping modes in supermicron nitrate mass size distributions could be identified. The lower mode, associated with sea-salt, was located between the surface-area and volume distribution of sodium peaking at about 2–3 m of EAD. The upper mode peaked at 3–5 m and followed more closely the surface-area distribution of calcium in all samples. At our site, the accumulation of nitrate into both particle types was shown to be limited by an effective surface reaction rate rather than by gas-phase diffusion. This rate was estimated to be considerably larger for sea-salt particles. Strong evidence in support of the saturation of nitrate in sea-salt particles were obtained.  相似文献