Análisis de los distintos procesos de interacción de los electrones con los componentes atmosféricos

En este trabajo se hace un análisis de los diferentes procesos de interacción de los electrones con los componentes atmosféricos determinándose para cada energía cuáles son predominantes y cuáles pueden ser despreciados. Como resultado se obtiene un modelo simplificado de la degradación energética de los electrones que permite además un ahorro importante en tiempo de computación.An analysis of the different excitation processes by which electrons interact with the atmospheric components is presented. The energy ranges in which they predominate or they can be neglected are determined. As a result, a simplified model of the energy degradation of electrons is- obtained that also implies a considerable reduction in the computing time.Asociación Argentina de Geofísicos y Geodesta

Un método simple para determinar la ionización correspondiente a los electrones secundarios y a los protones en un evento protónico

Los electrones generados por interacción de protones con los componentes atmosféricos juegan un rol preponderante en los efectos producidos eventos protónicos de altas energías. En este trabajo se presenta un modelo simple que permite separar en la ionización total producida en este tipo de fenómenos la contribución de los electrones generados y la correspondiente a los protones. Además se muestra como se obtiene el flujo de electrones en función de la altura y la energía a partir de la ionización producida por los mismos.The electrons generated in the interaction of protons with the atmospheric components play a fundamental rol in the effects that followed a high energy proton event. A simple model that allows to separate from the total ionization produced, the contribution due to electrons and protons, is presented. The way of obtaining the fluxes of electrons as a function of height and energy, from the ionization rates, is also showed.Asociación Argentina de Geofísicos y Geodesta

Algunas consideraciones sobre aspectos geométricos y atmosféricos en los canales ópticos de los sistemas satelitarios NOAA-AVHRR

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Rectificación espacial de imágenes multi-temporais del rio de la Plata y su frente oceanico obtenidas con el sistema NOAA-AVHRR

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OCEAN FEATURE DETECTION USING MICROWAVE BACKSCATTER AND SUN GLINT OBSERVATIONS

Synthetic Aperture Radar (SAR) satellite sensors have demonstrated their ability to observe ocean features related to dynamical processes including internal waves, currents, eddies, fronts, and the presence of bathymetric features. Because of the high resolution of available SAR sensors, circulation details and small-scale processes can be detected that are not observable by other sensors more frequently used for ocean research such as the NOAA AVHRR and the ORBVIEW2 SeaWiFS. In contrast to these, LANDSAT-TM thermal and optical channels can be used to observe sea surface temperatures, surface layer ocean color (upwelled radiance) as well as sun glint (reflected radiance) patterns of surface roughness at a spatial resolution comparable to that of SAR. Several examples of TM images obtained in 1997-2002 over the Argentine coastal ocean region where selected from an extensive data set. These images were analyzed and compared with a series of SAR images acquired over the same region by the ERS satellites and in some cases near coincident with the TM data. A close inspection of these data demonstrates that over a sun glint region, a high-resolution optical sensor can provide observations of sea surface patterns related to ocean dynamic processes very similar to those captured by SAR. The ability of TM to detect such ocean features can extend and complement the use of SAR data for ocean researc

ENVIRONMENTAL CHARACTERISTICS OF SAN MAT\ucdAS GULF OBTAINED FROM LANDSAT-TM AND ETM+ DATA

The San Matías Gulf, located between 40 47' S and 42 13' S on the Atlantic coast of South America, with an area of approximately 18 000 km², is the second largest in Argentina. This gulf has been studied by means of historical data obtained in oceanographic campaigns carried out before 1990 and with satellite images of low-resolution (1000 m) NOAA-AVHRR obtained from 1985. The analysis of this information permitted to infer some environmental characteristics related to temperature, salinity, productivity and circulation. The objective of the present work is to analyze LANDSAT-TM and ETM+ data from 1997-2003. Approximately 30 free of clouds images, obtained in different times of the year, were processed. The thermal channel allowed to obtain a detailed distribution of surface temperature, to identify thermal fronts and to analyze its variability along the year. Also, this channel and channel 1 permit to observe the influence, in the southern part of the gulf, of the water coming from the continental shelf and San José Gulf. The results obtained did not only contributed to corroborate the environmental characteristics already inferred previously from cruise data, but also, to identify others, so far unknow

Efecto de cubrimiento de nubes en la determinación de la temperatura supefficial de masas de água utilizando información del sensor AVHRR. Ejemplo: Rio de la Plata y su frente oceanico

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COMPARISON OF BATHYMETRIC FEATURES DETECTED BY ERS2 SAR AND LANDSAT TM DATA OVER SAN MAT\ucdAS GULF, ARGENTINA

It is well known that Synthetic Aperture Radar (SAR) is capable of imaging bathymetric features by detecting changes in sea surface roughness associated with bathymetry-induced surface current modulations. The high dynamic range of LANDSAT Thematic Mapper (TM) and Enhanced TM+ (ETM+) sensors allow them to observe oceanic surfaces affected by solar specular reflection, or sun glint, without being saturated. This ability allows the imaging of sea surface roughness patterns in the sun glint affected area that are associated with surface current changes such as those produced by bathymetric features. ERS SAR and LANDSAT TM/ETM+ images obtained over the San Matías Gulf, Argentina during similar tidal current conditions are compared and the surface signature generated by the interaction of the tidal current with the bottom topography analyzed. Each type of sensor presents advantages and limitations to the observation of bottom features due to the way each one detects sea surface roughness. Still, when sun glint is present, TM/ETM+ and SAR show similar bathymetric patterns under the same tidal conditions. While both sensors provide consistent information over significant bathymetry features, increased differences in the detection is observed over weaker feature

DETECTION OF SMALL-SCALE COASTAL OCEANOGRAPHIC PROCESSES THROUGH LANDSAT-TM/ETM+ IMAGES: IMPLICATIONS FOR THE STUDY OF BIOLOGICAL PROCESSES ALONG THE PATAGONIAN COASTS OF ARGENTINA

Gayana (Concepción) ISSN ABSTRACT The Argentine coastal zone, with its highly productive coastal waters, allows the existence of important seabird and marine mammal breeding assemblages, fish and crustacean spawning and nursery areas, and extensive macroalgae and mollusk beds. Knowledge of factors determining the dynamics of coastal waters is urgently needed to help understand their influence on biological processes and marine biodiversity. Available information in the region is currently scarce due to the low number of oceanographic cruises and oceanographic modeling studies. We evaluate the capacity of high-resolution satellite information for the identification and analysis of coastal processes such as fronts, upwellings, and small scale eddies. Using two case studies, we show how the analyses of temporal sequences of LANDSAT-TM and ETM+ images allow refining the formulation of biologica

Primary production in the Argentine Sea during spring estimated by field and satellite models

In satellite images of the world ocean the Argentine Sea is one of the areas of highest chlorophyll-a (Chl a) concentration. Here we analyze the spatial variability in primary production in relationship to phytoplankton biomass, and some relevant optical and physical characteristics observed during spring 2005. High Chl a concentrations were found in frontal areas, mainly at the shelf-break (19.0 mg m−3) and Grande Bay (28.6 mg m−3), with the lowest values offshore (0.4 mg m−3). Integrated production also varied widely from ∼275 to 5480 mg C m−2 d−1. Variations in the Chl a/in vivo-fluorescence, and photosynthetic parameters were related to the absorption characteristics of phytoplankton, indicating the influence of variations in the phytoplankton community composition. Surface Chl a explained only 51% of the variance in integrated primary production. Neither integrated production, nor the photosynthetic parameters were significantly related to seawater temperature. The simple satellite model used here resulted in significant underestimation of field primary production values (Absolute Percentage Difference > 50%). Our results indicate that a more adequate satellite model of production, making use of local photosynthetic parameters and vertical distribution of biomass, should be developed for this region.Fil: Lutz, Vivian A.. Instituto Nacional de Investigaciones y Desarrollo Pesquero; ArgentinaFil: Segura, Valeria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Subsede Instituto Nacional de Investigación y Desarrollo Pesquero; ArgentinaFil: Dogliotti, Ana Inés. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Gagliardini, Domingo Antonio. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Bianchi, Alejandro Ariel. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval. Departamento Oceanografía; ArgentinaFil: Balestrini, Carlos. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval. Departamento Oceanografía; Argentin