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91.
A. Warn-Varnas J. Hawkins K.G. Lamb S. Piacsek S. Chin-Bing D. King G. Burgos 《Ocean Modelling》2010,31(1-2):9-27
A high resolution modeling study is undertaken, with a 2.5-dimensional nonhydrostatic model, of the generation of internal waves induced by tidal motion over the ridges in Luzon Strait. The model is forced by the barotropic tidal components K1, M2, and O1. These tidal components, along with the initial density field, were extracted from data and models. As the barotropic tide moves over the Luzon Strait sills, there is a conversion of barotropic tidal energy into baroclinic tidal energy. Depressions are generated that propagate towards the Asian Seas International Acoustics Experiment (ASIAEX) test site on the Chinese continental shelf. Nonlinear effects steepen the depressions, frequency and amplitude dispersion set in, and disintegration into large amplitude solitary waves occurs. The effects of varying the initial density field, tidal component magnitudes, as well as adding a steady background current to represent the occasional excursions of the Kuroshio Current into the strait, are considered.Depressions are generated at each of the two sills in Luzon Strait which radiate away, steepening and evolving into internal solitary wave trains. Baroclinic fluxes of available potential energy, kinetic energy and linear are calculated for various parameter combinations. The solitary wave trains produced in the simulations generally consist of large amplitude wave trains alternating with small amplitude wave trains. During strong tidal flow, Kelvin–Helmholtz type instabilities can develop over the taller double-humped sill. The solitary waves propagating towards the ASIAEX test site have been observed to reach amplitudes of 120–250 m, depending on the tidal strength. ASIAEX observations indicate amplitudes up to 150 m and the Windy Island Experiment (WISE) measurements contain magnitudes over 200 m. The model results yield solitary wave amplitudes of 70–300 m and half widths of 0.60–3.25 km, depending on parameter values. These are in the range of observations. Measurements by Klymak et al. (2006), in the South China Sea, exhibit amplitudes of 170 m, half widths of 3 km and phase speeds of 2.9 m s?1. Model predictions indicate that the solitary waves making up the wave packet each experience different background currents with strong near surface shear.The energy in the leading soliton of the large amplitude wave trains ranges between 1.8 and 9.0 GJ m?1. The smaller value, produced using barotropic tidal currents based on the Oregon State University data base, is the same as the energy estimated to be in a solitary wave observed by Klymak et al. (2006). Estimates of the conversion of barotropic tidal energy into radiating internal wave energy yield conversion rates ranging between 3.6% and 8.3%. 相似文献
92.
In October 1862, Robert Mallet published an extensive study of a large earthquake that occurred on 16 December 1857, 150 km south-east of Naples. This event is one of the most destructive ever recorded in Italy. Although continental earthquakes of similar size are almost invariably associated with surface faulting, Mallet did not identify any surface rupture and subsequent workers have also failed to find surface traces. Using satellite images and aerial photographs as a guide, we examined two prominent Quaternary normal fault systems in the field. Flanking the Val d'Agri and the Val di Diano, both trend NW–SE and dip to the SW. The distribution of damage suggests that one or both moved in 1857. On one fault segment in Val d'Agri, we found a 2.5-m high scarp whose youthfulness and height suggest it is due to the 1857 earthquake. Comparison of the observed slip with rates derived from geomorphic evidence suggests a recurrence time for 1857 type events of about 3000 years. While the new data we provide are consistent with the event having a magnitude of M s ≈ 7.0, there are also grounds for supposing it might have been bigger. 相似文献
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95.
A. R. King M. E. Beer D. J. Rolfe K. Schenker J. M. Skipp 《Monthly notices of the Royal Astronomical Society》2005,358(4):1501-1504
We consider the population of black widow pulsars (BWPs). The large majority of these are members of globular clusters. For minimum companion masses ≲0.1 M⊙ , adiabatic evolution and consequent mass loss under gravitational radiation appear to provide a coherent explanation of all observable properties. We suggest that the group of BWPs with minimum companion masses ≳0.1 M⊙ are systems relaxing to equilibrium after a relatively recent capture event. We point out that all binary millisecond pulsars (MSPs) with orbital periods P ≲ 10 h are BWPs (our line of sight allows us to see the eclipses in 10 out of 16 cases). This implies that recycled MSPs emit either in a wide fan beam or a pencil beam close to the spin plane. Simple evolutionary ideas favour a fan beam. 相似文献
96.
A. R. King J. E. Pringle D. T. Wickramasinghe 《Monthly notices of the Royal Astronomical Society》2001,320(3):L45-L48
On the basis of the current observational evidence, we put forward the case that the merger of two CO white dwarfs produces both a Type Ia supernova explosion and a stellar remnant, the latter in the form of a magnetar. The estimated occurrence rates raise the possibility that many, if not most, Type Ia supernovae might result from white dwarf mergers. 相似文献
97.
A. R. King J. P. Osborne K. Schenker 《Monthly notices of the Royal Astronomical Society》2002,329(2):L43-L46
We show that the recently discovered short period supersoft source in M31 is probably a progenitor of a magnetic cataclysmic variable (CV). The white dwarf spins asynchronously because of the current high accretion rate. However its fieldstrength is typical of an AM Herculis system, which is what it will ultimately become. We discuss the relevance of this system to CV evolution, and its relation to some particular CVs with special characteristics. 相似文献
98.
C. A. Haswell R. I. Hynes A. R. King K. Schenker 《Monthly notices of the Royal Astronomical Society》2002,332(4):928-932
We compare ultraviolet (UV) spectra of the recent soft X-ray transients XTE J1118+480 and XTE J1859+226. The emission line strengths in XTE J1118+480 strongly suggest that the accreting material has been CNO processed. We show that this system must have come into contact with a secondary star of about 1.5 M⊙ , and an orbital period ∼15 h, very close to the bifurcation value at which the nuclear and angular momentum loss time-scales are similar. Subsequent evolution to the current period of 4.1 h was driven by angular momentum loss. In passing through a period of 7.75 h the secondary star would have shown essentially normal surface abundances. XTE J1118+480 could thus represent a slightly later evolutionary stage of A0620-00. We briefly discuss the broad Ly α absorption wings in XTE J1118+480. 相似文献
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