Editorial Appreciation     

Oddbjørn Engvold  Jack Harvey  John Leibacher  Takashi Sakurai  Zdeněk Švestka  Lidia van Driel-Gesztelyi 《Solar physics》2006,233(1):1-2

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Near inertial motion excited by wind change in a margin of the Typhoon 9019   总被引：1，自引：0，他引：1  

Akio Maeda  Kazuki Uejima  Toru Yamashiro  Masahito Sakurai  Hiroshi Ichikawa  Masaki Chaen  Keisuke Taira  Shinjirou Mizuno 《Journal of Oceanography》1996,52(3):375-388

An excitation of inertial oscillation in the upper layer east of course of Typhoon 9019 was fortuitously observed at three surface buoys deployed during the Ocean Mixed Layer Experiment (OMLET). The observed inertial oscillation was compared with wind fluctuation measured at Ocean Weather Station T (29°N, 135°E) which was placed at the center of a triangle with three vertexes occupied by the respective surface buoys. Inertial oscillation is effectively excited in the mixed layer at the eastern margin of the typhoon by a rapid decrease of wind rather than by prevailing strong wind. It is shown by means of a least square deviation that the inertial oscillation observed in the mixed layer has a period of 23.9 hours shorter than the local inertial period of 24.7 hours. This shorter period suggests that the inertial oscillation has the finite velocities of phase and group as an inertial internal wave. A theoretically obtained ratio of vertical component of group velocity to that of phase velocity, approximately agrees with observed value. The inertial internal wave is excited by fluctuation of divergence with near inertial period in the mixed layer.  相似文献   

Direct determination of barium in Sea water by inductively coupled plasma emission spectrometry     

Masahito Sugiyama  Masakazu Matsui  Eiichiro Nakayama 《Journal of Oceanography》1984,40(4):295-302

A method for the determination of barium in sea water was investigated using inductively coupled plasma emission spectrometry, and sea water samples from the Japan Sea and the Pacific Ocean were directly analyzed by this method. Artificial sea water was used to prepare matrix matched standard solutions to overcome the problem of physical interference. The detection limit (signal/noise ratio=2) for barium in deionized and distilled water was 0.08µg l^?1 and in sea water, 0.12µg l^?1. The reproducibilities in the purified water and in the sea water at the 10µg l^?1 level were 0.7% a#FFFFFFnd 0.5%, respectively. The barium concentration in both the Japan Sea and the Pacific Ocean increased with depth and ranged between 5.5–10.0µg l^?1 and 4.1–18.4µg l^?1, respectively.  相似文献   

An overview of the Oyashio ecosystem   总被引：3，自引：0，他引：3  

Yasunori Sakurai   《Deep Sea Research Part II: Topical Studies in Oceanography》2007,54(23-26):2526

The Oyashio shelf region and the seasonally ice-covered areas north of Hokkaido are highly productive, supporting a wide range of species including marine mammals, seabirds and commercially important species in the western subarctic Pacific. The fishes include gadids, such as walleye pollock and Pacific cod, and subarctic migratory pelagic fishes such as chum salmon and pink salmon. It is also an important summer feeding ground for subtropical migrants such as the Japanese sardine, Japanese anchovy, Pacific saury, mackerels, Japanese common squid, whales and seabirds. In recent decades, some components of the Oyashio ecosystem (i.e., phytoplankton, mesozooplankton, gadid fish, and subtropical migrants) have shown changes in species abundance or distribution that are correlated with environmental changes such as the 1976/1977 and 1988/1989 regime shifts. The First Oyashio Intrusion moved northward from the mid-1960s until the late 1970s, when it moved southward until the 1980s, after which it returned to the north again after the mid-1990s. The sea-surface temperature in spring decreased after the late 1970s, increased after the late 1980s, and remained high during the 1990s. The extent of ice cover in the Sea of Okhostk also decreased during the latest warming in the 1980–1990s but has increased again since the late 1990s. This and other variabilities affect the Oyashio ecosystem and the surrounding region.  相似文献   

Comparison of observed and theoretically calculated seiches of Heda Bay,Japan     

Taku Tada  Yoshinobu Tsuji  Masahito Tsukamoto  Yoshikazu Ueno  Masayuki Kawashima  Takashi Egawa  Yasuhiro Yamazaki 《Pure and Applied Geophysics》1992,138(2):309-322

We carried out observations of sea-level fluctuations simultaneously at three stations on the coast of Heda Bay, Honshu, Japan, using supersonic-type water level gauges controlled by a personal computer. Analyses of the obtained data showed predominant spectral peaks at periods of 7.6, 2.0 and 1.3 minutes for all three stations. Comparison of the observed data with numerically calculated normal oscillation modes of the bay indicates that these three spectral peaks correspond to the theoretical first, third and seventh normal modes of the basin respectively, judging from the results of cross-spectral analyses. The reason for the absence of the remaining normal modes, especially of the second or the lateral first mode of the basin, is briefly considered.  相似文献   

Analysis Of The Disappearing Filament And Flare Of 7 May 1992     

Y.H. Tang  Z. Mouradian  B. Schmieder  C. Fang  T. Sakurai 《Solar physics》1999,185(1):143-155

By using Yohkoh soft X-ray data, H filtergrams, and radio data, the activation of the disappearing filament and the flare eruption on 7 May 1992 have been studied. Main conclusions are as follows: (1) the emergence of new magnetic flux tends to affect the pre-existing X-ray loops, which usually appear in arcades spanning H filament, changing the magnetic environment of the filament, and then enhance the current in the filament. Therefore newly emerging flux plays a fundamental role in the destabilization of this filament. (2) According to the H data and the rising motion of the filament, the corresponding current variation in the filament has been calculated. It seems that the current interruption may be a possible trigger mechanism for this filament disappearance. (3) The magnetic field strength and the energy flux of energetic electrons in the source region of microwave bursts have been estimated by using the microwave spectrum. During the main phase, the mean magnetic strength and the energy flux of energetic electrons are about 300–400 G and 1×1011 erg cm–2 s –1, respectively. (4) The energy provided by reconnection of the current sheet and the total energy of the current filament are estimated and we show that there is enough energy stored in the filament to feed the 7 May, 1992 flare.  相似文献   

The acceleration and propagation of solar cosmic rays as deduced from the relative abundance of protons to helium nuclei     

Kunitomo Sakurai 《Solar physics》1971,17(2):459-467

Except for protons, the chemical composition of solar cosmic rays is very similar to the abundance of the elements at the photosphere of the Sun. If we consider the relative abundance ratio of protons to -particles (P/) at constant rigidity, this ratio is highly variable from one solar cosmic ray event to another. This ratio observed at the Earth, however, decreases monotonically with time from the onset of solar flares and, furthermore, is dependent on the heliocentric distance of the parent flares from the central meridian of the solar disk. P/'s which have been measured before the onset of SC geomagnetic storms change from 1.5 to 50 or more, being a function of the westward position of the source from the east limb of the Sun. These variations with respect to time and heliocentric distance suggest that the propagation of solar cosmic rays is strongly modulated in the interplanetary space. The major part of the -particles seem to propagate as if they are trapped within the magnetic clouds which produce SC geomagnetic and cosmic ray storms at the earth.The chemical composition and rigidity spectra of solar cosmic rays suggest that solar cosmic rays are mainly accelerated by the Fermi mechanism in solar flares. The observed variation of P/'s is produced mainly through the difference between the propagation characteristics of protons and -particles.NAS-NRC Associate with NASA.  相似文献   

Motion of sunspot magnetic fields and its relation to solar flares     

Kunitomo Sakurai 《Solar physics》1976,47(1):261-266

The magnetic polarity distributions in sunspot groups which produced solar proton flares have been analyzed. It is shown that the fluid motion in sunspot groups and below may be responsible for the origin of inverted or unusual polarity distributions, since rotating motion in these spot groups is often observed. Since such motion seems to produce twisting of magnetic field lines above sunspot groups, the origin of solar flares seems to be closely dependent on instability associated with this twisting of sunspot field lines in the chromosphere and the lower corona.  相似文献   

Growth of metric noise continuum storms and its relation to the source of microwave s-emissions     

Kunitomo Sakurai 《Planetary and Space Science》1975,23(9):1344-1346

The growth of radio noise continuum storms in metric frequencies or less is generally preceded by the appearance of the source of microwave S-emissions, which forms in complex sunspot groups as βγ or γ types. It is shown that the development of relationships between emissions is closely connected to the growth of magnetic field lines, above associated sunspot groups, into complex configurations.  相似文献   

Stray-Light Effect on Magnetograph Observations     

Chae  Jongchul  Yun  Hong Sik  Sakurai  Takashi  Ichimoto  Kiyoshi 《Solar physics》1998,183(2):229-244

To examine the stray-light effect in magnetograph observations, we have determined the point spread functions of the vector magnetograph mounted on the Japanese Solar Flare Telescope based on two indirect methods, one analyzing the solar limb intensity profile, and the other using the Fourier power spectra of photospheric intensity distributions. Point spread functions consist of two parts: a blurring part which describes seeing and small-spread-angle stray light, and a scattering part which describes large-spread-angle stray light. The FWHM spatial resolution is typically 3.0, and the amount of scattered light is about 15% on clear days. We find that the blurring part is well described by a Moffat function whose Fourier transform is given by an exponential function. Our results indicate that polarization measurements of low-intensity magnetic elements like sunspots may be significantly underestimated due to the large-spread-angle stray light, and polarization measurements of magnetic elements which are smaller than 5–7 appear to be disturbed by small-spread-angle stray light.  相似文献