UVB solar radiation climatology for Mexico

The measurement of solar B band Ultraviolet radiation (UVB) should be considered a priority in Mexico due to implications on public health throughout the country (total population, 108 million), but this is not carried out at present. Installed sensors cover only 0.12% of the country. However, there are alternative methods for estimating UVB radiation to overcome the lack of surface data. The most successful of these are based on the use of satellites for environmental monitoring. In the present work, UVB maps are constructed for the entire country using a single, daily satellite measurement of UVB at solar noon from 1978-2003. Satellite-derived values are compared with the ground measurements by a surface station located in Mexico City in order to validate the former. Wavelet spectrum analysis is employed to this end. A close correlation is observed between the two sets of data. Moreover, there is qualitative correspondence between the spatial distribution of the satellite-derived data and the surface topography. The difference resulting throughout the period mentioned is <2% of the average annual cumulative energy.     

Spectro-Polarimetric Observations and Non-Lte Modeling of Ellerman Bombs

Ellerman bombs are bright emission features observed in the wings of Hα, usually in the vicinity of magnetic concentrations. Here we show that they can also be detected in the Ca II infrared triplet lines, which are easier to interpret and therefore allow for more detailed diagnostics. We present full Stokes observations of the 849.8 and 854.2 nm lines acquired with the new spectro-polarimeter SPINOR. The data show no significant linear polarization at the level of 3 × 10⁻⁴. The circular polarization profiles exhibit measureable signals with a very intricate pattern of peaks. A non-LTE analysis of the spectral profiles emerging from these features reveals the presence of strong downflows (∼10 {km s⁻¹}) in a hot layer between the upper photosphere and the lower chromosphere. Visiting Astronomers, National Solar Observatory, operated by the Association of Universities for Research in Astronomy, Inc. (AURA), under cooperative agreement with the National Science Foundation. The National Center for Atmospheric Research (NCAR) is sponsored by the National Science Foundation, USA.     

A family of Coordinate Systems for Reissner-Nordstrom Geometry

In this work we integrate Einstein-Maxwell equations for a point charge, in a coordinate system first considered by Lake. The family of solutions obtained includes various well known metrics. A free metric function acting as a gauge in the solution, is related to the Lorentz contraction factor in infinity, considering a set of geodesic frames. This revised version was published online in July 2006 with corrections to the Cover Date.     

Dipolar magnetic moment of the bodies of the solar system and the Hot Jupiters

Context

The planets magnetic field has been explained based on the dynamo theory, which presents as many difficulties in mathematical terms as well as in predictions. It proves to be extremely difficult to calculate the dipolar magnetic moment of the extrasolar planets using the dynamo theory.

Objective

The aim is to find an empirical relationship (justifying using first principles) between the planetary magnetic moment, the mass of the planet, its rotation period and the electrical conductivity of its most conductive layer. Then this is applied to Hot Jupiters.

Method

Using all the magnetic planetary bodies of the solar system and tracing a graph of the dipolar magnetic moment versus body mass parameter, the rotation period and electrical conductivity of the internal conductive layer is obtained. An empirical, functional relation was constructed, which was adjusted to a power law curve in order to fit the data. Once this empirical relation has been defined, it is theoretically justified and applied to the calculation of the dipolar magnetic moment of the extra solar planets known as Hot Jupiters.

Results

Almost all data calculated is interpolated, bestowing confidence in terms of their validity. The value for the dipolar magnetic moment, obtained for the exoplanet Osiris (HD209458b), helps understand the way in which the atmosphere of a planet with an intense magnetic field can be eroded by stellar wind. The relationship observed also helps understand why Venus and Mars do not present any magnetic field.     

Influence of slow active faults in probabilistic seismic hazard assessment: the northwestern margin of the València trough

Areas of low strain rate are typically characterized by low to moderate seismicity. The earthquake catalogs for these regions do not usually include large earthquakes because of their long recurrence periods. In cases where the recurrence period of large earthquakes is much longer than the catalog time span, probabilistic seismic hazard is underestimated. The information provided by geological and paleo-seismological studies can potentially improve seismic hazard estimation through renewal models, which assume characteristic earthquakes. In this work, we compare the differences produced when active faults in the northwestern margin of the València trough are introduced in hazard analysis. The differences between the models demonstrate that the introduction of faults in zones characterized by low seismic activity can give rise to significant changes in the hazard values and location. The earthquake and fault seismic parameters (recurrence interval, segmentation or fault length that controls the maximum magnitude earthquake and time elapsed since the last event or T_e) were studied to ascertain their effect on the final hazard results. The most critical parameter is the recurrence interval, where shorter recurrences produce higher hazard values. The next most important parameter is the fault segmentation. Higher hazard values are obtained when the fault has segments capable of producing big earthquakes. Finally, the least critical parameter is the time elapsed since the last event (T_e), when longer T_e produces higher hazard values.     

A Comparative Quantitative Study of an Omani Soil Using X-Ray Diffraction Technique

Two methods for the quantification of clay minerals using X-ray diffraction techniques: the Constant Mineral Standards Method and the Constant Clay Method were applied to soil samples from Al-Khod (Northern Oman). The first method was based on the addition of different concentrations of clay to constant mineral standards while the latter was based on the additions of known internal standards to the clay sample. The clay investigated in this study contained montmorillonite, palygorskite, illite and kaolinite. The areas of the reflection peaks were found to relate linearly with additions of different proportions of clay or mineral standards. Using the two methods, the concentrations of the different components and their experimental errors were determined. From the errors and self consistency of the results obtained, and the practicality of sample preparation, it is proposed to use the Constant Mineral Standards Method.     

Acoustic mapping of fish aggregation areas to improve fisheries management in Las Perlas Archipelago,Pacific Panama

The purpose of this study was to investigate, characterize and map areas of the seabed of Las Perlas Archipelago (LPA), Republic of Panama using swath-bathymetry acoustic sonar techniques and to assess these methods as tools for feeding information into management zoning policy. In 2007 the LPA was granted conservation protection under national legislation. However, detailed management plans are still pending. Seabed mapping plays a fundamental role in identifying areas which should be prioritized within the management framework. Visual representation of habitat maps provides an effective medium for involving stakeholders in a co-management arena. In this survey, acoustically mapped areas of the seabed were ground-truthed using a combination of benthic grab samples, drop-down video and diver observations. The resulting mapped areas were then incorporated into a Geographic Information System (GIS) for further analysis. The output was a physical characterization of the seabed at three locations selected for being areas of high rugosity (habitat complexity) and, therefore, their potential importance as valuable fish aggregation sites. The rocky reefs and rhodolith beds identified in this survey represent particularly important fish aggregation and nursery habitats which should be considered priorities for protection under the management plans. This survey demonstrated the use of acoustic techniques to spatially resolve topographic features and physical characteristics of the seabed, illustrating their potential value as tools for fisheries management and marine reserve zoning in Las Perlas Archipelago and elsewhere.