Strong interplanetary field enhancements at Ulysses—evidence of dust trails' interaction with the solar wind?

Interplanetary field enhancements were first discovered in the vicinity of Venus. These events are characterised by an increase in the magnitude of the heliospheric magnetic field with a near-symmetrical, sometimes thorn-shaped profile, and last from minutes to hours. Surveys of the events near Venus and Earth indicated clustering of the events in inertial space, which suggested that their sources were Solar System objects other than the Sun. A survey is presented of strong events of this type detected by the Ulysses spacecraft from 1990 to late 2001. Most of the events are accompanied by a discontinuity in the field direction near the events' centres. Other discontinuities are often symmetrical about the enhancement. The majority of events last less than two hours. When examined as a whole, the events tend to be accompanied by subtle changes in some plasma parameters. The majority of the enhancements are accompanied by magnetic holes on their fringes. The enhancements' occurrence rate increases with decreasing heliocentric distance. Possible formation mechanisms are discussed. No link was found with solar, or solar wind sources. Several aspects of the survey results are consistent with an origin related to cometary dust trails. Possible processes associated with a dust-solar wind interaction are discussed.     

介质横向不均匀对震后地表位移场的影响

利用三维有限元模拟两层地球模型(包括弹性层和粘弹性层)介质的横向不均匀和断层错动的复杂性对震后地表位移场的影响，其数值结果包括弹性解和粘弹性解。结果表明，震后位移场的分布特征不仅与粘弹性层的流变特性有关，还与弹性层介质的剪切模量以及断层的同震错动有关。     

Origin of Fe-Ti Oxide Ores in Mafic Intrusions: Evidence from the Panzhihua Intrusion, SW China

Economic concentrations of Fe–Ti oxides occur as massive,conformable lenses or layers in the lower part of the Panzhihuaintrusion, Emeishan Large Igneous Province, SW China. Mineralchemistry, textures and QUILF equilibria indicate that oxidesin rocks of the intrusion were subjected to extensive subsolidusre-equilibration and exsolution. The primary oxide, reconstructedfrom compositions of titanomagnetite in the ores and associatedintergrowths, is an aluminous titanomagnetite (Usp₄₀) with 40wt % FeO, 34 wt % Fe₂O₃, 16·5 wt % TiO₂, 5·3 wt% Al₂O₃, 3·5 wt % MgO and 0·5 wt % MnO. This compositionis similar to the bulk composition of the oxide ore, as inferredfrom whole-rock data. This similarity strongly suggests thatthe ores formed from accumulation of titanomagnetite crystals,not from immiscible oxide melt as proposed in earlier studies.The occurrence of oxide ores in the lower parts of the Panzhihuaintrusion is best explained by settling and sorting of densetitanomagnetite in the ferrogabbroic parental magma. This magmamust have crystallized Fe–Ti oxides relatively early andabundantly, and is likely to have been enriched in Fe and Tibut poor in SiO₂. These features are consistent with fractionationof mantle-derived melts under relatively high pressures (10kbar), followed by emplacement of the residual magma at 5 kbar.This study provides definitive field and geochemical evidencethat Fe–Ti oxide ores can form by accumulation in ferrogabbro.We suggest that many other massive Fe–Ti oxide depositsmay have formed in a similar fashion and that high concentrationsof phosphorus or carbon, or periodic fluctuation of fO₂ in themagma, are of secondary importance in ore formation. KEY WORDS: ELIP; Fe–Ti oxide ore; layered intrusion; Panzhihua; QUILF     

Historical space as narrative medium: on the configuration of spatial narratives of time at historical sites

This paper examines how narratives of history are organized spatially at historical sites and memorial spaces, especially in urban settings and in places invested with a sense of collective memory. Much recent research has focused on landscape, memory, and place and how relationships of political and social power influence the representation of historical events in public spaces. Although the meaning of such sites may be hotly contested for long periods of time, we focus here on narrative theory and the related, but unexplored, issue of how such historical stories are configured on the ground at actual historical sites. We identify a number of narrative strategies which are frequently used to configure historical stories in space. Declamatory strategies using markers presenting a snapshot of an event are common, but sequential and non-sequential linear strategies are also used, as are thematic strategies that cross-cut space and time to present complex historical stories at various spatial scales. Examples are drawn from a range of historical sites in North America, Europe and Israel.     

A General Linear Wave Theory for Water Waves Propagating over Uneven Porous Bottoms

Starting from the widespread phenomena of porous bottoms in the near shore region, considering fully the diversity of bottom topography and wave number variation, and including the effect of evanescent modes, a general linear wave theory for water waves propagating over uneven porous bottoms in the near shore region is established by use of Green‘s scond identity. This theory can be reduced to a number of the most typical mild-slope equations curreutly in use and provide a reliable research basis for follow-up development of nonlinear water wave theory involving porous bottoms.     

Acoustic plane-wave scattering from a rough surface over a random fluid medium

Acoustic plane-wave scattering from a rough surface overlying a fluid half-space with a sound-speed distribution subject to a small random variation is considered. Under the assumption that the surface roughness and medium randomness are statistically independent, the scattered field may be derived by first solving for the mean field in the medium, and then incorporating with boundary-perturbation method to obtain the total mean field and the power spectral density of the scattered field. The employed algorithm is compatible to the analysis available in the existing literature so that the formulations are conveniently integrated. The results for the power spectral density have shown that the effects of medium inhomogeneities on the rough surface scattering are limited in a spectral regime where the scattered components have shallow grazing angles. The distribution of the power spectral density over the space is primarily governed by the power spectrum and correlation lengths of the rough surface.