Variable stars in the Magellanic Clouds: results from OGLE and SIRIUS     

Yoshifusa Ita  Toshihiko Tanabé  Noriyuki Matsunaga  Yasushi Nakajima  Chie Nagashima  Takahiro Nagayama  Daisuke Kato  Mikio Kurita  Tetsuya Nagata  Shuji Sato  Motohide Tamura  Hidehiko Nakaya  Yoshikazu Nakada 《Monthly notices of the Royal Astronomical Society》2004,347(3):720-728

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Evapotranspiration and runoff in a forest watershed,western Japan     

A. Shimizu  T. Shimizu  Y. Miyabuchi  Y. Ogawa 《水文研究》2003,17(15):3125-3139

A Note has been published for this article in Hydrological Processes 18(4) 2004, 825. Both water and heat balances were studied in a conifer plantation watershed in south‐west Japan, within the warm‐temperate East Asia monsoon area. Forest cover in the watershed consists mainly of Japanese cedar (Cryptomeria japonica) and Japanese cypress (Chamaecyparis obtusa) plantations. Precipitation and runoff have been observed since 1991, so evapotranspiration can be compared with the water balance. Two meteorological observation towers were built to monitor evapotranspiration in the watershed. The annual average precipitation, amount of runoff and losses were 2166, 1243 and 923 mm, respectively. The evapotranspiration (latent heat flux) agreed well with the water balance losses. The average annual evapotranspiration at the tower built in the centre of the watershed was 902 mm; evapotranspiration at the other tower, further upslope, was 875 mm. The observed evapotranspiration was 39% to 40% of the average precipitation (2166 mm). The mean net radiation was c. 2·6 GJ m^?2 year^?1, and is considered a representative value of the net radiation (Rn) in coniferous plantations in this region. This region is classified in the humid zone based on the ratio of net radiation (Rn) to the energy required to evaporate the rainfall (λR). The mean annual evaporation of canopy‐intercepted water was 356 mm or about 15% of the average precipitation. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

The structure of cometary atmospheres     

Mikio Shimizu 《Astrophysics and Space Science》1976,40(2):243-251

The distributions of various kinds of molecular ions in the atmospheres of new and old comets made up from dirty ice of the second kind (H₂O ice and hydrate clathrates of CO and N₂) have been computed at various heliocentric distances, by taking into account photoionization, ionmolecular reactions, electron-ion recombinations, and some transport effects. The results have been compared with observations and other computations. It is argued that dirty ice of the second kind model will impose a restriction on the theory of the origin of the solar system.  相似文献   

Oxygen isotopic anomaly and solar nebular photochemistry     

Y. Kitamura  M. Shimizu 《Earth, Moon, and Planets》1983,29(2):199-202

At the cool periphery of the solar nebula, oxygen could photochemically be formed from water. The mixing of¹⁷O and¹⁸O enriched by the self-shielding effect of¹⁶O₂ to the dust grain melted by the shock waves there would explain the oxygen isotopic anomaly in the high-temperature mineral of the carbonaceous meteorites.  相似文献   

Comparison of toxicity between populations of Gonyaulax tamarensis of eastern North American waters     

Lucie Maranda  Donald M. Anderson  Yuzuru Shimizu 《Estuarine, Coastal and Shelf Science》1985,21(3):401-410

Isolates of the dinoflagellate Gonyaulax tamarensis were established from benthic cysts or motile cells collected along the north-western Atlantic coast from the Bay of Fundy to Long Island. All clones were grown under the same conditions and assayed in a blind test for toxin content and composition. Differences in toxin content (μmouse unit per cell) spanning two orders of magnitude were found, with decreasing toxicity from north to south. Some isolates had undetectable toxin levels. The low toxicity of southern strains of G. tamarensis may explain the historical absence of paralytic shellfish poisoning (PSP) in areas where cysts and motile cells have been reported. The cause of the observed geographic pattern is unknown, but is does suggest that there may be an environmentally-determined southern limit to the regional PSP problem.Qualitative data on the toxin composition of some clones indicate that saxitoxin, neosaxitoxin and gonyautoxins -II, -III and -IV are generally present. A more quantitative approach (i.e. one which examines each isolate for all of the 12 Gonyaulax toxins) is needed to fully utilize the potential of toxin composition in discriminating between strains.  相似文献   

Buoyancy-driven perturbations in a rapidly rotating,electrically conducting fluid: part I – flow and magnetic field     

David E. Loper  Arnaud Chulliat  Hisayoshi Shimizu 《地球物理与天体物理流体动力学》2013,107(6):429-469

The steady velocity, perturbation pressure and perturbation magnetic field, driven by an isolated buoyant parcel of Gaussian shape in a rapidly rotating, unconfined, incompressible electrically conducting fluid in the presence of an imposed uniform magnetic field, are obtained by means of the Fourier transform in the limit of small Ekman number. Lorentz and inertial forces are neglected. The solution requires at most evaluation of a single integral and is found in closed form in some spatial regions. The solution has structure on two disparate scales: on the scale of the buoyant parcel and on the scale of the Taylor column, which is elongated in the direction of the rotation axis. The detailed structures of the flow and pressure depend linearly on the relative orientation of gravity and rotation, with the solution for arbitrary orientation being a linear combination of two limiting cases in which these vectors are colinear (polar case) and perpendicular (equatorial case). The perturbation magnetic field depends additionally on the relative orientation of the imposed magnetic field, and three limiting cases of interest are presented in which gravity and rotation are colinear (polar–toroidal case), gravity and imposed field are colinear (equatorial–radial case) and all three are mutually perpendicular (equatorial–toroidal case). Visualization and analysis of the velocity and perturbation magnetic field vectors are facilitated by dividing these vector fields into geostrophic and ageostrophic protions. In all cases, the geostrophic and ageostrophic portions have different structure on the Taylor-column scale. The buoyancy force is balanced by a pressure force in the polar case and by a flux of momentum in the equatorial case. The pressure force and momentum flux do not decay in strength with increasing axial distance. Far from the parcel, the axial mass flux varies as the inverse one-third power of distance from the parcel. The velocity has a single geostrophic vortex in the polar case and two vortices in the equatorial case. The perturbation magnetic field has two, four and one geostrophic vortices in the polar–toroidal, equatorial–radial and equatorial–toroidal cases, respectively. To facilitate comparison of the present results with numerical simulations carried out in a finite domain, a set of boundary conditions are developed, with may be applied at a finite distance from the parcel.  相似文献   

Polarization Calibration of the Solar Optical Telescope onboard Hinode     

K. Ichimoto  B. Lites  D. Elmore  Y. Suematsu  S. Tsuneta  Y. Katsukawa  T. Shimizu  R. Shine  T. Tarbell  A. Title  J. Kiyohara  K. Shinoda  G. Card  A. Lecinski  K. Streander  M. Nakagiri  M. Miyashita  M. Noguchi  C. Hoffmann  T. Cruz 《Solar physics》2008,249(2):233-261

The Solar Optical Telescope (SOT) onboard Hinode aims to obtain vector magnetic fields on the Sun through precise spectropolarimetry of solar spectral lines with a spatial resolution of 0.2 – 0.3 arcsec. A photometric accuracy of 10⁻³ is achieved and, after the polarization calibration, any artificial polarization from crosstalk among Stokes parameters is required to be suppressed below the level of the statistical noise over the SOT’s field of view. This goal was achieved by the highly optimized design of the SOT as a polarimeter, extensive analyses and testing of optical elements, and an end-to-end calibration test of the entire system. In this paper we review both the approach adopted to realize the high-precision polarimeter of the SOT and its final polarization characteristics.  相似文献   

The Solar Optical Telescope for the Hinode Mission: An Overview     

S. Tsuneta  K. Ichimoto  Y. Katsukawa  S. Nagata  M. Otsubo  T. Shimizu  Y. Suematsu  M. Nakagiri  M. Noguchi  T. Tarbell  A. Title  R. Shine  W. Rosenberg  C. Hoffmann  B. Jurcevich  G. Kushner  M. Levay  B. Lites  D. Elmore  T. Matsushita  N. Kawaguchi  H. Saito  I. Mikami  L. D. Hill  J. K. Owens 《Solar physics》2008,249(2):167-196

The Solar Optical Telescope (SOT) aboard the Hinode satellite (formerly called Solar-B) consists of the Optical Telescope Assembly (OTA) and the Focal Plane Package (FPP). The OTA is a 50-cm diffraction-limited Gregorian telescope, and the FPP includes the narrowband filtergraph (NFI) and the broadband filtergraph (BFI), plus the Stokes Spectro-Polarimeter (SP). The SOT provides unprecedented high-resolution photometric and vector magnetic images of the photosphere and chromosphere with a very stable point spread function and is equipped with an image-stabilization system with performance better than 0.01 arcsec rms. Together with the other two instruments on Hinode (the X-Ray Telescope (XRT) and the EUV Imaging Spectrometer (EIS)), the SOT is poised to address many fundamental questions about solar magnetohydrodynamics. This paper provides an overview; the details of the instrument are presented in a series of companion papers. M. Otsubo is a former NAOJ staff scientist.  相似文献   

The Solar Optical Telescope of Solar-B (Hinode): The Optical Telescope Assembly     

Y. Suematsu  S. Tsuneta  K. Ichimoto  T. Shimizu  M. Otsubo  Y. Katsukawa  M. Nakagiri  M. Noguchi  T. Tamura  Y. Kato  H. Hara  M. Kubo  I. Mikami  H. Saito  T. Matsushita  N. Kawaguchi  T. Nakaoji  K. Nagae  S. Shimada  N. Takeyama  T. Yamamuro 《Solar physics》2008,249(2):197-220

The Solar Optical Telescope (SOT) aboard the Solar-B satellite (Hinode) is designed to perform high-precision photometric and polarimetric observations of the Sun in visible light spectra (388 – 668 nm) with a spatial resolution of 0.2 – 0.3 arcsec. The SOT consists of two optically separable components: the Optical Telescope Assembly (OTA), consisting of a 50-cm aperture Gregorian with a collimating lens unit and an active tip-tilt mirror, and an accompanying Focal Plane Package (FPP), housing two filtergraphs and a spectro-polarimeter. The optomechanical and optothermal performance of the OTA is crucial to attain unprecedented high-quality solar observations. We describe in detail the instrument design and expected stable diffraction-limited on-orbit performance of the OTA, the largest state-of-the-art solar telescope yet flown in space.  相似文献   

Image Stabilization System for Hinode (Solar-B) Solar Optical Telescope     

T. Shimizu  S. Nagata  S. Tsuneta  T. Tarbell  C. Edwards  R. Shine  C. Hoffmann  E. Thomas  S. Sour  R. Rehse  O. Ito  Y. Kashiwagi  M. Tabata  K. Kodeki  M. Nagase  K. Matsuzaki  K. Kobayashi  K. Ichimoto  Y. Suematsu 《Solar physics》2008,249(2):221-232

The Hinode Solar Optical Telescope (SOT) is the first space-borne visible-light telescope that enables us to observe magnetic-field dynamics in the solar lower atmosphere with 0.2 – 0.3 arcsec spatial resolution under extremely stable (seeing-free) conditions. To achieve precise measurements of the polarization with diffraction-limited images, stable pointing of the telescope (<0.09 arcsec, 3σ) is required for solar images exposed on the focal plane CCD detectors. SOT has an image stabilization system that uses image displacements calculated from correlation tracking of solar granules to control a piezo-driven tip-tilt mirror. The system minimizes the motions of images for frequencies lower than 14 Hz while the satellite and telescope structural design damps microvibration in higher frequency ranges. It has been confirmed from the data taken on orbit that the remaining jitter is less than 0.03 arcsec (3σ) on the Sun. This excellent performance makes a major contribution to successful precise polarimetric measurements with 0.2 – 0.3 arcsec resolution. K. Kobayashi now at NASA/Marshall Space Flight Center, Huntsville, AL 35812, USA.  相似文献