Search

In this study, radon-222 concentrations were measured within 34 houses distributed in the northern, southern, and central areas of the city of Queretaro in 2007. The objective of this study was to establish the spatial distribution of radon with respect to geological faults and its relation to certain environmental variables. For each sampling site, the radon-222 concentration was analyzed as a function of various climate variables, relative humidity, temperature, and atmospheric pressure, in addition to the ventilation of the house and distance of each site from any geological faults in the area. A multivariate statistical technique was used to analyze these variables based on two components. For component 1, the relative humidity and temperature had the greatest weight, 0.677 and 0.492, respectively, while for component 2, the greatest weights corresponded to radon and the temperature with 0.693 and 0.609, respectively. The average radon concentration across the entire sampling period was 38.92 Bq/m3, the minimum detected value was 6.01 Bq/m3 for site 91GAG0607, and the maximum detected value was 225.95 Bq/m3 for site 91CAM20907. This last value is outside the standards permitted by the Environmental Protection Agency of the United Stated, which is 148 Bq/m3 for indoor environments. With respect to geological faults and their relationship to radon-222, the concentrations for the sampling sites had no relationship to the closeness or distance to these faults.

A partir de las observaciones de una perturbación en el medio interplanetario, se discuten dos posibles fuentes de rayos cósmicos solares: los más energéticos son generados en el propio proceso de origen del destello en Ha asociado a la perturbación, los de menor energía son generados en el frente de onda de la perturbación. Se hace un estimado de la distancia en que se produce la activación del mecanismo de generación en el frente de onda.

First results of ULF geomagnetic anomalies observed at the Tlamacas station (98deg 37' 41" W, 19deg 04' 01" N) located at 4 km near the volcano Popocatepetl (active volcano, 98.62 W, 19.02 N) for the period March-July, 2005 and their analysis are presented. The geomagnetic data were collected by a 3-axial fluxgate magnetometer designed at UCLA, (1 Hz sampling rate frequency, GPS). Our analysis reveals some anomalies, which are suspected to be generated by the local volcanic origin: the EM background in the vicinity of the volcano is significantly noisier than in other reference stations; the sporadic strong noise-like geomagnetic activity observed in the H-component; some geomagnetic pulsations (without preferred polarization) observed only at the Tlamacas station. Also the dynamics of the geomagnetic fractal index for the Tlamacas station in a comparison with the reference station points out to the some changes in critical processes, which may occur in the vicinity of the volcano.

A penetration of electric and magnetic fields of global electromagnetic ELF resonances in the cavity Earth-ionosphere into the ionosphere is investigated numerically. It is shown that a penetration depth for magnetic components is 2-3 times greater than for electric ones and it depends essentially on the orientation of the geomagnetic field with respect to the normal to the Earth's surface. A penetration height for the electric field is about 50/spl divide/60 km, for magnetic field it is 100/spl divide/150 km.

Results of the ULF electromagnetic emission during earthquake (EQ) swarm and Izu-Miyake volcano eruption at summer period of 2000 are presented and analyzed. Analysis of the obtained data has been performed in 3 main directions: traditional statistical analysis i.e. analysis of time dynamics of spectral density, polarization ratios and their derivatives, principal component analysis and fractal analysis. Statistical characteristics were studied at different frequency sub-bands in a frequency range 10-3-0.3 Hz. The mentioned methods of data processing are described and obtained results are illustrated and discussed. Some peculiarities of obtained results such as rise of the second principal component and rise of fractal index can be interpreted as a possible short-time precursors

Se reportan los avances en la construcción de un arreglo plano de 64X64 (4096) dipolos de onda completa, con una frecuencia de operación de 140 MHz ocupando un área de 10 000 m² (70 m x 140 m) para realizar observaciones de centelleo interplanetario (CIP). Este será un arreglo dedicado de tiempo completo a estudios de CIP donde se espera captar diariamente cerca de 1000 fuentes de radio conocidas. El arreglo se está construyendo en Coeneo, Michoacán (localizado a 350 km de la Ciudad de México, Lat. 19°48’ N, Long. 101°41’ O y a 1964 m sobre el nivel del mar). El MEXART (por sus siglas en inglés) tendrá algunas características similares al arreglo del MRAO en Cambridge, pero con varias mejoras tales como un mejor sistema electrónico, frecuencia de operación más alta, una parte trasera digital y su ubicación en una altitud geomagnética intermedia (29°). El proyecto MEXART consiste de dos etapas. En la primera se construyó un arreglo prototipo cerca de la ciudad de México, el cual tenía todos los elementos básicos de la antena del arreglo final, pero cubriendo un área menor (1000 m²) y con una matriz de Butler de 4x4. En la segunda etapa estamos construyendo el arreglo final con la asistencia técnica del NCRA-TIFR de la India. El MEXART será el único instrumento de su tipo en el continente americano y formará parte de una red junto con otros observatorios de CIP en otras longitudes como el ORT en la India y el STEL en Japón. Esta red de observatorios de CIP proporcionará información relevante para el estudio de las perturbaciones de gran escala que se propagan en el medio interplanetario, en particular las que tiene mayor relevancia al clima espacial. Esperamos iniciar observaciones a principios de 2003.