Sources of intense geomagnetic storms over the rise of solar cycle 23

In this work we present a study of the triggers of intense geomagnetic storms since the launch of the WIND spacecraft, November 1995 until December 2001. Reviewing the signatures of solar wind flow, we looked for two different kinds of interplanetary events associated with intense geomagnetic storms: ejecta and corotating solar wind streams. We also looked for the solar origin related to both events. We provide a list of the solar–terrestrial events during the rising phase of this solar cycle. The paper includes statistical conclusions that shed light onto the paradigm of geomagnetic storms.     

Visual binary star orbits in universal variables

In this paper, we make use of the Stumpff's functions to solve the problem of determining the orbit of a visual binary star in universal variables. The method is thus valid for all types of orbits: hyperbolic, parabolic and elliptic.     

Asymptotic solutions of the restricted problem near the equilateral Lagrangian points

The restricted problem in the vicinity of the Lagrangian point L₄ is studied by finding a convergent binomial expansion of the disturbing function. Using a Hamiltonian formulation in Delaunay variables and removing the short-period terms a resonance problem (already considered by Giacaglia (1970) in an attempt of enlarging the Ideal Resonance) is obtained. It is shown that this extension is reducible to Garfinkel's ideal resonance in the libration region.     

Minette mafic microgranular enclaves and their relationship to host syenites in systems formed at mantle pressures: major and trace element evidence from the Piquiri Syenite Massif, southernmost Brazil

Summary Mafic microgranular enclaves in the ultrapotassic Piquiri Syenitic Massif (611 ± 1 Ma) in southern Brazil represent a minette magma mingled with a syenitic one, both produced from similar mantle sources and emplaced in a post-collisional setting of Neoproterozoic age. The minette magma is compositionally close to typical minettes and high-SiO₂ lamproites, with relatively high contents of LREE, Cs and Rb. It is slightly silica-undersaturated, ultrapotassic and metaluminous, with K₂O/Na₂O ratios around 2–3, and about 4–7 wt% K₂O. The Piquiri minettes contain K-clinopyroxene and pyrope, which are interpreted to have crystallized under pressures about 5 GPa. Whole-rock and mineral chemistry indicate that the most suitable source for the minette magma is clinopyroxene-phlogopite-apatite-amphibole-sulphide ± garnet mantle veins, under pressures of about 5 GPa and melting temperatures over 1,000 °C. Fractional melting is admitted in order to explain the extremely high Rb, Cs and LREE contents of the minette melt, and is consistent with its estimated rheological behavior. The syenitic host-rock parental magma was produced from a similar source, probably at lower pressures, and the co-mingling probably occurred still at large depth, under pressures around 3 GPa. Rheological and geochemical considerations support a model based on fractional melting of a veined mantle which had been metasomatized during previous (760–700 Ma) ocean-plate consumption. The subduction-related metasomatism in the source is indicated by low LREE/(Nb or Ta) ratios, high Nb/Ta and U/Th ratios, and low Ti contents. The compositional similarity and close spatial and temporal association of minette and syenitic magmas can be explained by their common source region. Compared to typical lamproitic magmatism, the major difference is that the Piquiri minette magmas are derived from a subduction-modified source.     

Where are the broad lines in Seyfert 2s?

The unified model for Seyfert 2s postulates that these galaxies are in fact normal Seyfert ls whose innermost regions are hidden from a direct view by an opaque torus. Galaxies seen from a line-of-sight within the opening angle of this torus have the central continuum source and the Broad Line Region unobstructed, and are classified as Seyfert 1/QSO. In Seyfert 2s, on the other hand, periscopic views of the hidden nucleus may be obtained through scattering of the nuclear light in the extranuclear regions. If this model is correct, the Blue and Featureless Continuum observed in many Seyfert 2s is simply a mirror image of the obscured nucleus. In this case, the light from the Broad Line Region must also be reflected towards the observer. Seyfert 2s should therefore exhibit broad lines in their spectrum, which, by definition, they do not! In this contribution we examine this issue and the complications it brings to the basic unification picture of Seyfert galaxies. We fail to find a consistent explanation for this question in the framework of the unified model. An alternative modified-unified model for Seyfert 2s is proposed.