Mixing process on the northeast coast of Hokkaido in summer

Direct measurements using a free-falling micro-profiler were conducted on the northeast coast of Hokkaido in the summer of 2007 to clarify the mixing process in the Soya Warm Current (SWC) region in terms of microstructure. The distribution of the Turner angle (Tu) showed that these regions have a high potential for double diffusive convection, but direct measurements of the turbulent dissipation rate (ε) and dissipation of temperature variance ( $ \chi_{T} $ ) did not necessarily correspond to each other in the SWC region, especially in the offshore front of SWC and farther offshore. The mixing efficiency indicated that, even though the Turner angle (Tu) indicated a high potential for double diffusive convection, turbulent mixing was the main contributor to the mixing process in this region, and double-diffusive convection only contributed partially and sparsely, especially in the boundary off SWC water. The bottom mixed layer (BML) is known to thicken off the SWC. The vertical diffusivity coefficient was enhanced near the bottom (10^?4–10^?3 m² s^?1) off the SWC, and these results support that turbulence near the bottom off the SWC contributed to the thickening of the BML.     

Magnetodynamic phenomena in the solar and stellar outer atmospheres

Magnetic effects causing anomalous heating and drastic flarings in the atmospheres of various types of stars are discussed. The best studied examples of these magnetic effects with spatially resolved observations are those in the case of the Sun, but no simple application of the solar knowledge to the stellar cases is allowed, since there are generally very large differences in the physical conditions between the Sun and other types of stars. We examine possible effects of the magnetic field in the respective situations of several types of stars which show X-ray and radio emissions indicating the presence of such activities, and it is concluded that the magnetic field may be playing important roles in producing anomalous heating and drastic flarings also in those stars having very different physical conditions, in ways seemingly very different from, but intrinsically closely related to, those in the case of the Sun.Invited review paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.     

Chromospheric activity of late-type giants and supergiants: Reappearance of dynamo activity in the interior due to the spin-up of the core in evolution

The renewal of chromospheric activity in red giants and supergiants is interpreted in terms of the reappearance of dynamo activity in the interior due to the spin-up of the core caused by its contraction in the course of evolution from the main sequence to the giant stage. A region of very high rotational shear (differential rotation) develops between the core, which spins up by a large factor through the drastic contraction, and the envelope, which spins down in contrast by virtue of expansion. Mechanisms of angular momentum transfer may operate to smear this large shear, and bring the inner part of the envelope into sheared rotation. A convective layer, on the other hand, develops in the envelope from the surface inwards, when the envelope expands and the temperature is lowered. A dynamo layer, or a layer in which the sheared rotation co-exists with the convection (the presence of a remnant magnetic field being postulated), will thus reappear in the inner part of the envelope when the envelope-convection reaches down and invades the layer of sheared rotation. Surface chromospheric activity due to the magnetic field is thus renewed when the regenerated magnetic field is brought up to the surface by the envelope-convection. These phenomena occur as the star evolves into the giant stage and hence explain the observed characteristic of gradual revival of chromospheric activity from the subgiant to the giant stage. Visiting Scientist at the Tokyo Astronomical Observatory under the support of the Japan Society for the Promotion of Sciences. On leave from the Indian Institute of Astrophysics. Deceased on 1982 August 19     

台风涌浪传播的计算方法

本文推导出一个计算台风涌浪传播的较普遍的公式,实例计算表明,所推得的公式较好地反映了台风涌浪传播的主要特征.     

Neutron Activation Analysis of Nine GSJ Sedimentary Rock Reference Samples

Nine rock reference samples "Sedimentary rock series" issued by the Geological Survey of Japan (GSJ) were analysed for up to 31 elements by neutron activation analysis (NAA); 14MeV-NAA for Si and Al, fission track method for U, radiochemical and instrumental NAA for rare-earth elements, and instrumental NAA for the remaining elements, with reactor neutrons for the latter three. The present results are compared with reported values.     

Laboratory Study of O(1S) Formation Process in the Photolysis of O3 and its Atmospheric Implications

A high-sensitive technique to detect O(¹S) atoms using vacuum ultraviolet laser-induced fluorescence (VUV-LIF) spectroscopy has been applied to study the O(¹S) production process from the UV photodissociation of O₃, N₂O, and H₂O₂. The quantum yields for O(¹S) formation from O₃ photolysis at 215 and 220 nm are determined to be (1.4 ± 0.4) × 10⁻⁴ and (5 ± 3) × 10⁻⁵, respectively. Based on thermochemical considerations, the O(¹S) formation from O₃ photolysis at 215 and 220 nm is attributed to a spin-forbidden process of O(¹S)+O₂(X³Σ_g ⁻). Analysis of the Doppler profile of O(¹S) produced from O₃ photolysis at 193 nm also indicates that the O(¹S) atoms are produced from the spin-forbidden process. In the photolysis of N₂O and H₂O₂ at 193 nm, no discernible signal of O(¹S) atoms has been detected. The upper limit values of the quantum yields for O(¹S) production from N₂O and H₂O₂ photolysis at 193 nm are estimated to be 8 × 10⁻⁵ and 3 × 10⁻⁵, respectively. Using the experimental results, the impact of the O(¹S) formation from O₃ photolysis on the atmospheric OH radical formation through the reaction of O(¹S)+H₂O has been estimated. The calculated results show that the contribution of the O(¹S)+H₂O reaction to the OH production rate is ∼2% of that of the O(¹D)+H₂O reaction at 30 km altitude in mid-latitude. Implications of the present laboratory experimental results for the terrestrial airglow of O(¹S) at 557.7 nm have also been discussed.     

Formation of astrophysical jets by a contracting magnetic accretion disk

In the present paper, we discuss an MHD model for the formation of astrophysical jets, in which the directed flows are ejected along the rotation axis of an accretion disk formed from a cloud having a large scale magnetic field parallel to the angular momentum axis of the disk. The acceleration of jets is due to thej×B force in the relaxing magnetic twist which is produced by the rotation of the disk. The characteristic features of the jets, predicted by our mechanism and hopefully to be proven by observations, are the helical velocity and the hollow cylindrical shape of the jet, with a diameter of roughly the size of the region from which the acceretion disk collected its mass. Justification for the assumption of the perpendicular orientation of the disk, or the parallelism of the jets, to the external magnetic field may be provided by the fact that the component of rotation whose axis is perpendicular to the field may have been damped in the earlier phase of the cloud contraction.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 Septemper–6 October, 1984.     

Simultaneous seeing measurement through the Subaru Telescope in the visible and near-infrared bands for the wavelength dependence evaluation

Stellar images have been obtained under natural seeing at visible and near-infrared wavelengths simultaneously through the Subaru Telescope at Mauna Kea. The image quality is evaluated by the full-width at the half-maximum (FWHM) of the stellar images. The observed ratio of FWHM in the V-band to the K-band is 1.54 ± 0.17 on average. The ratio shows tendency to decrease toward bad seeing as expected from the outer scale influence, though the number of the samples is still limited. The ratio is important for simulations to evaluate the performance of a ground-layer adaptive optics system at near-infrared wavelengths based on optical seeing statistics. The observed optical seeing is also compared with outside seeing to estimate the dome seeing of the Subaru Telescope.