Three-mode Cepheid pulsation     

T. Ishida  M. Saitou 《Astrophysics and Space Science》1991,182(1):69-74

We simulated two models of classical Cepheids with the same effective temperature and luminosity but different masses. Neither model has significant resonance among linear nonadiabatic periods of the fundamental, the first overtone, and the second overtone radial modes. The higher mass model found to approach to the second overtone-only state. The lower mass model shows a complicated three-mode interaction and none of the amplitudes of three modes is negligible. The relation of the higher mass model to the shortest period Cepheid HR 7308, and that of the lower mass model to the double-mode Cepheids are discussed. It appears that three-mode nonresonant coupling should be considered to explain the behaviours of both models.  相似文献   

Coupling modes of hydromagnetic oscillations in non-uniform, finite pressure plasmas: Two-fluids model     

Tsutomu Tamao 《Planetary and Space Science》1978,26(12):1141-1148

Within a framework of the two-fluids approximation, basic modes constituting hydromagnetic coupling oscillations in non-uniform, finite-β plasmas are examined. It is shown that the oscillations consist of a coupling between a localized mode and a propagating one, and a strong peak appears at a resonance point. In the case of isothermal plasma (T_e = T_i), there are two localized modes, the Alfvén (or drift Alfvén) and the ion drift modes, and a propagating mode being known as the fast magnetosonic wave. Coupling oscillations associated with the Alfvén mode exhibit a nearly incompressible character, whereas those with the ion drift mode are compressional and diamagnetic. Furthermore, the slow magnetosonic wave also couples with the localized mode in the case of T_e > T_i. Based on characteristics of these oscillations, the origin of geomagnetic pulsations is discussed in connection with the distribution of plasma parameters in the outer magnetosphere.  相似文献   

Three-mode Cepheid pulsation     

T. Ishida 《Astrophysics and Space Science》1990,168(2):243-252

Amplitude equations, that are used in the investigation of stellar pulsations, for the three-mode nonresonant coupling case are inferred from that of the two-mode nonresonant coupling case. Characteristics of the fixed points of the amplitude equations are studied. Chaotic behaviour is expected when the amplitude equations consist of more than two modes.  相似文献   

A criterion of double-mode pulsation from coupling coefficients     

T. Ishida 《Astrophysics and Space Science》1990,167(1):173-176

A criterion for the occurrence of double-mode pulsations is derived from linear adiabatic coupling coefficients The criterion indicates that double-mode pulsations of classical Cepheids occur at a shorter period range than the observed one, and that the evolutionary mass models are preferable for the double-mode pulsations.  相似文献   

Interaction of energetic particles with HM-waves in the magnetosphere     

Tsutomu Tamao 《Planetary and Space Science》1984,32(11):1371-1386

Energetic particle response in electromagnetic fields of ULF HM-waves in the magnetosphere is reviewed. Pc4–5 geomagnetic pulsations observed at the synchronous altitude are classified into three types, in respect to their major magnetic field polarization in different directions, local time dependence, and different characteristics of accompanied flux modulations of energetic particles, i.e., two nearly transverse waves with the azimuthal and the radial polarization, and the compressional stormtime pulsations. Firstly, we formulate the drift kinetic theory of particle flux modulations under the constraint of the magnetic moment conservation. A generalized energy integral of the particle motion interacting with a ULF-wave with the three-dimensional structure propagating to the azimuthal direction is obtained in the L-shell coordinate of a mirror magnetic field. Its linearized form is reduced to the same form as the previously derived energy change, including the bounce-drift resonant interaction. It is shown that the perturbed guiding center distribution function of energetic particles consists of four contributions, the adiabatic mirror effect corresponding to pitch-angle change, the kinetic effects due to energy change and the accompanying L-shell displacement, and the bounceaveraged drift phase bunching. Secondly, the basic HM-wave modes constitutingcoupling ULF oscillations in non-uniform plasmas are discussed in different models of approach for different plasma states. The diamagnetic drift Alfvén wave and the compressional drift wave with a larger azimuthal mode number in a high-beta plasma are candidates for the stormtimes pulsations. The former is intrinsically a guided localized mode, while the latter is a non-localized mode. By making use of the above preparation, we apply the developed drift kinetic theory to interpret the phase relationships between the ion flux modulation and the geomagnetic pulsation in some selected examples of observations, demonstrating a fair agreement in theoretical results with the observations.  相似文献   

Western Arctic primary productivity regulated by shelf-break warm eddies     

Eiji Watanabe  Michio J. Kishi  Akio Ishida  Maki Noguchi Aita 《Journal of Oceanography》2012,68(5):703-718

The response of phytoplankton to the Beaufort shelf-break eddies in the western Arctic Ocean is examined using the eddy-resolving coupled sea ice–ocean model including a lower-trophic marine ecosystem formulation. The regional model driven by the reanalysis 2003 atmospheric forcing from March to November captures the major spatial and temporal features of phytoplankton bloom following summertime sea ice retreat in the shallow Chukchi shelf and Barrow Canyon. The shelf-break warm eddies spawned north of the Barrow Canyon initially transport the Chukchi shelf water with high primary productivity toward the Canada Basin interior. In the eddy-developing period, the anti-cyclonic rotational flow along the outer edge of each eddy moving offshore occasionally traps the shelf water. The primary production inside the warm eddies is maintained by internal dynamics in the eddy-maturity period. In particular, the surface central area of an anti-cyclonic eddy acquires adequate light, nutrient, and warm environment for photosynthetic activity partly attributed to turbulent mixing with underlying nutrient-rich water. The simulated biogeochemical properties with the dominance of small-size phytoplankton inside the warm eddies are consistent with the observational findings in the western Arctic Ocean. It is also suggested that the light limitation before autumn sea ice freezing shuts down the primary production in the shelf-break eddies in spite of nutrient recovery. These results indicate that the time lag between the phytoplankton bloom in the shelf region following the summertime sea ice retreat and the eddy generation along the Beaufort shelf break is an important index to determine biological regimes in the Canada Basin.  相似文献   

When did cosmic acceleration start? How fast was the transition?     

mille E.O. Ishida  Ribamar R.R. Reis  Alan V. Toribio  Ioav Waga 《Astroparticle Physics》2008,28(6):547-552

Cosmic acceleration is investigated through a kink-like expression for the deceleration parameter (q). The new parametrization depends on the initial (q_i) and final (q_f) values of q, on the redshift of the transition from deceleration to acceleration (z_t) and the width of such transition (τ). We show that although supernovae (SN) observations (Gold182 and SNLS data samples) indicate, at high confidence, that a transition occurred in the past (z_t > 0) they do not, by themselves, impose strong constraints on the maximum value of z_t. However, when we combine SN with the measurements of the ratio between the comoving distance to the last scattering surface and the SDSS + 2dfGRS BAO distance scale (S_k/D_v) we obtain, at 95.4% confidence level, and for (S_k/D_v+Gold182), and and for (S_k/D_v+SNLS), assuming q_i = 0.5 and q_f = −1. We also analyze the general case, q_f  (−∞, 0) finding the constraints that the combined tests (S_k/D_v+SNLS) impose on the present value of the deceleration parameter (q₀).  相似文献   

Modulation of energetic particle fluxes due to long-period geomagnetic oscillations     

Tsutomu Tamao 《Planetary and Space Science》1978,26(12):1149-1159

Mechanism of flux modulations of energetic protons and electrons, associated with the long-period geomagnetic pulsations in the outer magnetosphere, is examined theoretically. In the first part, a linear perturbation theory of the guiding centre distribution function averaged over the bounce phase of an interacting particle is developed for the case of the three-dimensional magnetic oscillations with a sufficiently long period compared with the bounce time of the particle. Secondly we extend the formulation to include some effects of the perturbed drift orbit on the particle distribution such as the particle trapping in the wave field and the phase bunching process. The latter is important for the interaction with the coupling Alfvén mode of magnetic oscillations. Applying these results together with the basic characteristics of the coupling hydromagnetic oscillations in a non-uniform plasma, we discuss the possibilities for the observed particle flux modulations in two different cases, separately, i.e. flux oscillations due to the compressional magnetic perturbation and those from the nearly transverse magnetic variations.  相似文献   

Heat-Mitigation Effects of Irrigated Rice-Paddy Fields Under Changing Atmospheric Carbon Dioxide Based on a Coupled Atmosphere and Crop Energy-Balance Model     

Ikawa  Hiroki  Kuwagata  Tsuneo  Haginoya  Shigenori  Ishigooka  Yasushi  Ono  Keisuke  Maruyama  Atsushi  Sakai  Hidemitsu  Fukuoka  Minehiko  Yoshimoto  Mayumi  Ishida  Sachinobu  Chen  Charles P.  Hasegawa  Toshihiro  Watanabe  Tsutomu 《Boundary-Layer Meteorology》2021,179(3):447-476

Boundary-Layer Meteorology - Known as the heat-mitigation effect, irrigated rice-paddy fields distribute a large fraction of their received energy to the latent heat during the growing season. The...  相似文献   

X-ray photoelectron spectroscopic study on the goethites with variations in crystallinity and morphology: their effects on surface hydroxyl concentration   总被引：1，自引：0，他引：1  

Takuya Echigo  Tamao Hatta  Seiko Nemoto  Shigeru Takizawa 《Physics and Chemistry of Minerals》2012,39(9):769-778

We examined the effects of crystallinity and crystal morphology on surface hydroxyl concentration of goethite using four kinds of goethite samples prepared by aging a hydrous ferric oxide (ferrihydrite) at different temperatures ranging from 4 to 70?°C. These samples were analyzed with the following methods: powder X-ray diffraction, Brunauer–Emmett–Teller surface area analyzer, atomic force microscopy, attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and high-resolution X-ray photoelectron spectroscopy (XPS). The first three analyses showed that the goethite aged at lower temperature has lower crystallinity, smaller particle size and lower aspect ratio. The ATR-FTIR analysis revealed that the OH-stretching band of goethite aged at 4?°C moves to slightly higher wavenumber than those of the samples aged at higher temperatures. Their XPS analyses demonstrated that variation in the concentration of surface hydroxyl group ranges from 6.6 (nm^?2) for the sample aged at 4?°C to 7.7 (nm^?2) for the sample aged at 70?°C. Considering the analytical depth of the XPS (~5?nm), photoelectrons are emitted from the uppermost layers of the analyte. Hence, XPS results are interpreted to reflect variations in the morphology of fine crystals (<100?nm thick). The morphology of the present goethites can be characterized by their aspect ratio, in other words, the degree of development of (110)–(110) intersection edges at which protons preferentially accumulate. This variation in the concentration of surface hydroxyl group revealed by XPS analysis offers experimental evidence for the effects of crystallinity and morphology on the surface chemical properties of goethite.  相似文献