Catalogue of unambiguous (Faraday-thin,one-component,spectrum-selected) rotation measures for galaxies and quasars

This all-sky catalogue of unambiguous rotation measure (from a Faraday-thin, one-component, spectrum selection) for 674 galaxies or quasars has been compiled, ordered, and edited from the available literature. All the known applications of the RM distribution toward foreground objects in the Galaxy (i.e., magnetic field in 4 nearby spiral arms and in 4 nearby interstellar magnetic bubbles) have also been catalogued.     

Chain of galaxies in centaurus

Further photometric and spectroscopic observations of a chain of galaxies in Centaurus are presented and discussed.     

Giant CP Stars?

This study is part of an investigation of the possibility of using chemically peculiar (CP) stars to map local galactic structure. Correct luminosities of these stars are therefore crucial. CP stars are generally regarded as main-sequence or near-main-sequence objects. However, some CP stars have been classified as giants. A selection of stars, classified in literature as CP giants, are compared to normal stars in the same effective temperature interval and to ordinary ‘non giant’ CP stars. We find no clear confirmation of a higher luminosity for ‘CP giants’, than for CP stars in general. In addition, CP characteristics seem to be individual properties not repeated in a component star or other cluster members.     

Experiments with CP stars

Described here is a preliminary and tentative application of a method for fine-classification of stars, selected for studies of galactic structure. The present investigation is based on about 100 stars within the approximate spectral type range B6-A5, for which both spectra andUBV photometry have been obtained. The motivation of the project is the following: For the study of galactic fine-structure it is essential to use as many members as possible of stellar agglomerations of various type for a statistical treatment of the material. A-type stars are fairly numerous and reasonably bright, but if all chemically peculiar stars, fast rotators or multiple systems have to be omitted there is generally too little left for a relevant investigation. Here we perform some experiments in order to find a method for fine-classification of A stars, both normal and chemically peculiar, within the framework of the M K system. In this connection it is desirable to reduce the present multitude of CP classifications to a manageable number. It is shown here that, independenttly of the definition of the degree of peculiarity, there is no sharp borderline separating the CP stars from the ‘normal’ ones. Also it is found that spectral classification can on an average be performed with almost the same accuracy for CP stars as for the ‘normal’ ones provided cases of extreme peculiarity are avoided. Based on observations collected at European Southern Observatory, La Silla, Chile.     

The solar wind velocity in the eleven-year cycle no. 20 and the solar radar cross-section

The annual average values of the solar wind velocity over the period 1962–1972 were investigated on the basis of data obtained from different space probes. The comparison of the pattern of the annual average solar wind velocities observed by the Vela and Pioneer 6 satellites indicates that the pattern presented by Gosling et al. (1971) is realistic. The long-range trend in the solar wind velocity during the 11-year cycle is governed by the number and intensity of irregularities occurring in the corona. These irregularities may represent motions of mass or some types of MHD shock waves and they are responsible for the increased heating of the corona which then in turn causes an increase in the values of the solar radar cross-section and of the solar wind velocity. A close relation is demonstrated between the monthly and annual average values of the solar wind velocity and of the cross-section.     

Magnetization of celestial bodies with special application to the primeval Earth and Moon

The magnetic fields of celestial bodies are usually supposed to be due to a ‘hydromagnetic dynamo’. This term refers to a number of rather speculative processes which are supposed to take place in the liquid core of a celestial body. In this paper we shall follow another approach which is more closely connected with hydromagnetic processes well-known from the laboratory, and hence basically less speculative. The paper should be regarded as part of a general program to connect cosmical phenomena with phenomena studied in the laboratory. As has been demonstrated by laboratory experiments, a poloidal magnetic field may be increased by the transfer of energy from a toroidal magnetic field through kink instability of the current system. This mechanism can be applied to the fluid core of a celestial body. Any differential rotation will produce a toroidal field from an existing poloidal field, and the kink instability will feed toroidal energy back to the poloidal field, and hence amplify it. In the Earth-Moon system the tidal braking of the Earth's mantle acts to produce a differential angular velocity between core and mantle. The braking will be transferred to the core by hydromagnetic forces which at the same time give rise to a strong magnetic field. The strength of the field will be determined by the rate of tidal braking. It is suggested that the magnetization of lunar rocks from the period ?4 to ?3 Gyears derives from the Earth's magnetic field. As the interior of the Moon immediately after accretion probably was too cool to be melted, the Moon could not produce a magnetic field by hydromagnetic effects in its core. The observed lunar magnetization could be produced by such an amplified Earth field even if the Moon never came closer than 10 or 20 Earth's radii. This hypothesis might be checked by magnetic measurements on the Earth during the same period.     

Preliminary Quantitative Assessment of Earthquake Casualties and Damages

Prognostic estimations of the expected number of killed or injured people and about the approximate cost associated with the damages caused by earthquakes are made following a suitable methodology of wide-ranging application. For the preliminary assessment of human life losses due to the occurrence of a relatively strong earthquake we use a quantitative model consisting of a correlation between the number of casualties and the earthquake magnitude as a function of population density. The macroseismic intensity field is determined in accordance with an updated anelastic attenuation law, and the number of casualties within areas of different intensity is computed using an application developed in a geographic information system (GIS) environment, taking advantage of the possibilities of such a system for the treatment of space-distributed data. The casualty rate, defined as the number of killed people divided by the number of inhabitants of the affected region, is also computed and we show its variation for some urban concentrations with different population density. For a rough preliminary evaluation of the direct economic cost derived from the damages, equally through a GIS-based tool, we take into account the local social wealth as a function of the gross domestic product of the country. This last step is performed on the basis of the relationship of the macroseismic intensity to the earthquake economic loss in percentage of the wealth. Such an approach to the human casualty and damage levels is carried out for sites near important cities located in a seismically active zone of Spain, thus contributing to an easier taking of decisions in emergency preparedness planning, contemporary earthquake engineering and seismic risk prevention.     

Inverse problem in hydrogeology

The state of the groundwater inverse problem is synthesized. Emphasis is placed on aquifer characterization, where modelers have to deal with conceptual model uncertainty (notably spatial and temporal variability), scale dependence, many types of unknown parameters (transmissivity, recharge, boundary conditions, etc.), nonlinearity, and often low sensitivity of state variables (typically heads and concentrations) to aquifer properties. Because of these difficulties, calibration cannot be separated from the modeling process, as it is sometimes done in other fields. Instead, it should be viewed as one step in the process of understanding aquifer behavior. In fact, it is shown that actual parameter estimation methods do not differ from each other in the essence, though they may differ in the computational details. It is argued that there is ample room for improvement in groundwater inversion: development of user-friendly codes, accommodation of variability through geostatistics, incorporation of geological information and different types of data (temperature, occurrence and concentration of isotopes, age, etc.), proper accounting of uncertainty, etc. Despite this, even with existing codes, automatic calibration facilitates enormously the task of modeling. Therefore, it is contended that its use should become standard practice.

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Resumen Se sintetiza el estado del problema inverso en aguas subterráneas. El énfasis se ubica en la caracterización de acuíferos, donde los modeladores tienen que enfrentar la incertidumbre del modelo conceptual (principalmente variabilidad temporal y espacial), dependencia de escala, muchos tipos de parámetros desconocidos (transmisividad, recarga, condiciones limitantes, etc), no linealidad, y frecuentemente baja sensibilidad de variables de estado (típicamente presiones y concentraciones) a las propiedades del acuífero. Debido a estas dificultades, no puede separarse la calibración de los procesos de modelado, como frecuentemente se hace en otros campos. En su lugar, debe de visualizarse como un paso en el proceso de entendimiento del comportamiento del acuífero. En realidad, se muestra que los métodos reales de estimación de parámetros no difieren uno del otro en lo esencial, aunque sí pueden diferir en los detalles computacionales. Se discute que existe amplio espacio para la mejora del problema inverso en aguas subterráneas: desarrollo de códigos amigables al usuario, acomodamiento de variabilidad a través de geoestadística, incorporación de información geológica y diferentes tipos de datos (temperatura, presencia y concentración de isótopos, edad, etc), explicación apropiada de incertidumbre, etc. A pesar de esto, aún con los códigos existentes, la calibración automática facilita enormemente la tarea de modelado. Por lo tanto, se sostiene que su uso debería de convertirse en práctica standard.

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Résumé Létat du problème inverse des eaux souterraines est synthétisé. Laccent est placé sur la caractérisation de laquifère, où les modélisateurs doivent jouer avec lincertitude des modèles conceptuels (notamment la variabilité spatiale et temporelle), les facteurs déchelle, plusieurs inconnues sur différents paramètres (transmissivité, recharge, conditions aux limites, etc.), la non linéarité, et souvent la sensibilité de plusieurs variables détat (charges hydrauliques, concentrations) des propriétés de laquifère. A cause de ces difficultés, le calibrage ne peut être séparé du processus de modélisation, comme cest le cas dans dautres cas de figure. Par ailleurs, il peut être vu comme une des étapes dans le processus de détermination du comportement de laquifère. Il est montré que les méthodes dévaluation des paramètres actuels ne diffèrent pas si ce nest dans les détails des calculs informatiques. Il est montré quil existe une large panoplie de techniques d ‹inversion : codes de calcul utilisables par tout-un-chacun, accommodation de la variabilité via la géostatistique, incorporation dinformations géologiques et de différents types de données (température, occurrence, concentration en isotopes, âge, etc.), détermination de lincertitude. Vu ces développements, la calibration automatique facilite énormément la modélisation. Par ailleurs, il est souhaitable que son utilisation devienne une pratique standardisée.