Interpretation of the infrared polarization of Venus     

Sonoyo Mukai  Tadashi Mukai 《Icarus》1979,38(1):90-99

A contradiction in the sulfuric acid cloud hypothesis of Venus, i.e., nondetection of 4.8 μm polarization by Landau (1975), is examined on the basis of the multiple scattering calculations for the cloud model of Hansen and Hovenier (1974) including an internal heat source. Results show that the polarized thermal component cannot depolarize the scattered sunlight, and therefore a large polarization of about 13% is expected at a phase angle of 110° and wavelength of 4.8 μm, in contrast with Landau's measurements. Our computations are, however, in agreement with the measurements by S. Sato et al. (in “Proceedings, 10th Lunar and Planetary Symposium,” pp. 179–182. Institute of Space and Aeronautical Science, University of Tokyo, July 11–13, 1977).  相似文献   

Quaternary folding of the eastern Tian Shan, northwest China   总被引：3，自引：0，他引：3  

Bihong Fu  Aiming Lin  Ken-ichi Kano  Tadashi Maruyama  Jianming Guo 《Tectonophysics》2003,369(1-2):79-101

The Tian Shan, east–west trending more than 2000 km, is one of most active intracontinental mountain building belts that resulted from India–Eurasia collision during Cenozoic. In this study, Quaternary folding related to intracontinental mountain building of the Tian Shan orogenic belt is documented based on geologic interpretation and analyses of the satellite remote sensing images [Landsat Thematic Mapper (TM)/Enhanced Thematic Mapper (ETM) and India Remote Sensing (IRS) Pan] combined with field geologic and geomorphic observations and seismic reflection profiles. Analyses of spatial–temporal features of Quaternary folded structure indicate that the early Quaternary folds are widely distributed in both piedmont and intermontane basins, whereas the late Quaternary active folds are mainly concentrated on the northern range-fronts. Field observations indicate that Quaternary folds are mainly characterized by fault-related folding. The formation and migration of Quaternary folding are likely related to decollement surfaces beneath the fold-and-fault zone as revealed by seismic reflection profiles. Moreover, analysis of growth strata indicates that the Quaternary folding began in late stage of early Pleistocene (2.1–1.2 Ma). Finally, tectonic evolution model of the Quaternary deformation in the Tian Shan is presented. This model shows that the Quaternary folding and faulting gradually migrate toward the range-fronts due to the continuous compression related to India–Eurasia collision during Quaternary time. As a result, the high topographic relief of the Tian Shan was formed.  相似文献   

Origin of scattered disk resonant TNOs: Evidence for an ancient excited Kuiper belt of 50 AU radius     

Patryk Sofia Lykawka  Tadashi Mukai 《Icarus》2007,186(2):331-341

Resonance occupation of trans-neptunian objects (TNOs) in the scattered disk (>48 AU) was investigated by integrating the orbits of 85 observed members for 4 Gyr. Twenty seven TNOs were locked in the 9:4, 16:7, 7:3, 12:5, 5:2, 8:3, 3:1, 4:1, 11:2, and 27:4 resonances. We then explored mechanisms for the origin of the resonant structure in the scattered disk, in particular the long-term 9:4, 5:2, and 8:3 resonant TNOs (median 4 Gyr), by performing large scale simulations involving Neptune scattering and planetary migration over an initially excited planetesimals disk (wide range of eccentricities and inclinations). To explain the formation of Gyr-resident populations in such distant resonances, our results suggest the existence of a primordial planetesimal disk of at least 45-50 AU radius that suffered a dynamical perturbation leading to 0.1-0.3 or greater eccentricities and a range of inclinations up to ∼20° during early stages of the Solar System history, before planetary migration.  相似文献   

Discovery of Jurassic ammonoids from the Shyok suture zone to the northeast of Chang La Pass, Ladakh, northwest India and its tectonic significance   总被引：1，自引：0，他引：1  

Masayuki  Ehiro  Satoru  Kojima  Tadashi  Sato  Talat  Ahmad  Tomoyuki  Ohtani 《Island Arc》2007,16(1):124-132

Abstract   Callovian (late Middle Jurassic) ammonoids Macrocephalites and Jeanneticeras were recovered from the Shyok suture zone, northeast of Chang La Pass, Ladakh, northwest India. They are the first reliable Jurassic fossils and the oldest chronologic data from the Shyok suture zone. The ammonoid-bearing Jurassic strata, newly defined as the Tsoltak Formation, consist largely of terrigenous mudstone with thin sandstone beds and were probably a part of the continental basement to the Cretaceous Ladakh Arc.  相似文献   

Tsunami Assessment for Risk Management at Nuclear Power Facilities in Japan     

Ken Yanagisawa  Fumihiko Imamura  Tsutomu Sakakiyama  Tadashi Annaka  Tomoyoshi Takeda  Nobuo Shuto 《Pure and Applied Geophysics》2007,164(2-3):565-576

The present study focuses on evaluation of the maximum and minimum water levels caused by tsunamis as risk factors for operation and management at nuclear power facilities along the coastal area of Japan. Tsunamis generated by submarine earthquakes are examined, basing literature reviews and databases of information on historical tsunami events and run-up heights. For simulation of water level along the coast, a numerical calculation system should be designed with computational regions covering a particular site. Also the calculation system should be verified by comparison of historical and calculated tsunami heights. At the beginning of the tsunami assessment, the standard faults, their locations, mechanisms and maximum magnitudes should be carefully estimated by considering historical earthquake-induced tsunamis and seismo-tectonics at each area. Secondly, the range of errors in the model parameters should be considered since earthquakes and tsunamis are natural phenomena that involve natural variability as well as errors in estimating parameters. For these reasons, uncertainty-induced errors should be taken into account in the process of tsunami assessment with parametric study of the tsunami source model. The element tsunamis calculated by the standard fault models with the errors would be given for the design. Then, the design tsunami can be selected among the element tsunamis with the most significant impact, maximum and minimum water levels, on the site, bearing in mind the possible errors in the numerical calculation system. Finally, the design tsunami is verified by comparison with the run-up heights of historical tsunamis, ensuring that the design tsunami is selected as the highest of all historical and possible future tsunamis at the site.  相似文献   

The abundance of helium in prominences and in the chromosphere     

Tadashi Hirayama 《Solar physics》1971,19(2):384-400

The abundance of helium relative to hydrogen is spectroscopically determined in prominences and in the chromosphere by using 1952, 1958, 1962 and 1966 eclipse data. Care is taken in the intensity calibration of emission lines, the self-absorption, and the departure from local thermodynamic equilibrium. We find from the line profiles and intensities of prominences and the chromosphere that the neutral helium lines are emitted in the metal-hydrogen emitting region where the kinetic temperature is low enough, 6000 8000 K, so that only the ionization due to UV radiation from the corona can explain the intensity of neutral helium emission. Also we find that the intensity ratio of Hei 3888.65 to H₈ 3889.05 increases towards the upper boundaries of prominences and of the chromosphere and that it approaches to a universal limiting value, both in various prominences or in the chromosphere, where it is considered that the ionization of neutral helium and hydrogen is nearly complete. From these facts the helium to hydrogen number ratio is found to be 6.5 ± 1.5%.A new schematic model of the chromosphere is presented where spicules have no hot region of emitting neutral helium lines. Here it is suggested that the kinetic temperature of spicules, 6000 8000 K, would be primarily determined by the radiation temperature of the corona and the transition region beyond the Lyman continuum of hydrogen which happens to be around those temperatures.  相似文献   

Crystallization temperature determination of Itokawa particles by plagioclase thermometry with X‐ray diffraction data obtained by a high‐resolution synchrotron Gandolfi camera     

Masahiko Tanaka  Tomoki Nakamura  Takaaki Noguchi  Aiko Nakato  Hatsumi Ishida  Toru Yada  Kei Shirai  Akio Fujimura  Yukihiro Ishibashi  Masanao Abe  Tatsuaki Okada  Munetaka Ueno  Toshifumi Mukai 《Meteoritics & planetary science》2014,49(2):237-244

The crystallization temperatures of Itokawa surface particles recovered by the space probe Hayabusa were estimated by a plagioclase geothermometer using sodic plagioclase triclinicity. The Δ131‐index required for the thermometer, which is the difference in X‐ray diffraction peak positions between the 131 and 11 reflections of plagioclase, was obtained by a high‐resolution synchrotron Gandolfi camera developed for the third generation synchrotron radiation beamline, BL15XU at SPring‐8. Crystallization temperatures were successfully determined from the Δ131‐indices for four particles. The observed plagioclase crystallization temperatures were in a range from 655 to 660 °C. The temperatures indicate crystallization temperatures of plagioclases in the process of prograde metamorphism before the peak metamorphic stage.  相似文献   

The influence of the brightness of the asteroidal dust bands on the gegenschein     

Tadashi Mukai  Masanori Fujino  Ryosuke Nakamura  Fumihiko Usui 《Icarus》2003,162(2):337-343

The position and shape of the Gegenschein’s maximum brightness provide information on the structure of the interplanetary dust cloud. We show that the asteroidal dust bands, extended near the anti-solar point, play an important role in determining both the position of the maximum brightness and the shape of the Gegenschein. After removing the asteroidal dust bands from an observation of the Gegenschein on November 2, 1997, it was found that the maximum brightness point shifted −0.4° in ecliptic latitude, i.e., to the south of the ecliptic plane, at an ecliptic longitude of 180°, in contrast to a latitude value of +0.1° when the dust bands were included. Furthermore, the part of the Gegenschein to the south of the ecliptic plane was brighter than the northern part at the time of observation. Referring to the cloud model of T. Kelsall et al. (1998, Astrophy. J. 508, 44-73), it can be estimated that the ascending node of the symmetry plane of the dust cloud is 57°^−3°_+7° when its inclination is 2.03° ? 0.50°.  相似文献   

Some instabilities in the 3/1 and 2/1 resonances     

Tadashi Yokoyama  Massae Sato  Masayoshi Tsuchida 《Celestial Mechanics and Dynamical Astronomy》1987,41(1-4):99-105

In a very simple way, it is possible to show the existence of small regions of instability, inside the observed 3/1 and 2/1 Kirkwood Gap, by using the classical Laplace-Lagrange secular theory.  相似文献   

Packing effect of fluffy particles     

T. Mukai  H. Fechtig 《Planetary and Space Science》1983,31(6):655-658

Packing forces, produced by an anisotropic sublimation of mantle material of grains located at the surface layer of loosely conglomerated fluffy particles, move the grains towards the center of the fluffy particles. This leads to a reduction of the empty space inside the fluffy particle and consequently to an increase of the mass density of the fluffy particle with time.As observed by the Helios dust experiment, fluffy particles of low density are ejected by comets with high eccentricity e and large semimajor axis a Since e and a of fluffy particles decrease with time due to the Poynting-Robertson effect, the accompanying increase of the density of fluffy particles seems to explain the existence of normal dense particles in quasi-circular orbits as detected during in situ measurements. It also explains that the majority of lunar craters have been produced by normal dense particles rather than by low density particles.  相似文献