Contribución a la cinemática del anticiclón del Pacífico sur

A partir de tres bases de datos climáticos diferentes para el Océano Pacífico Sur, se determina la evolución anual de la posición media mensual del Centro del Anticiclón del Pacífico (CAP) y la de la presión correspondiente. Se comparan entre sí loe resultados obtenidos y se extraen las características comunes más importantes. Se utilisan los valores medios mensuales de la presión de Isla de Pascua (27°10' S; 109°76' O) e Isla Juan Fernández (33°37' S; 78°52' O), para comprobar algunas de estas características y afinar otras. Se discute dichas características y se asocian a los rasgos fundamentales del lugar de presión media mensual máxima en Chile SLPM). A través del LPM se asocian algunas características del clima de Chile a las del CAP. Se pone de relieve el rol directo que juega la evolución de la latitud media mensual del CAP en esas características del clima.The annual evolutions of both monthly mean position and pressure oí the Pacific Anticyclone Centre (PAO) are determined using three South Pacific Ocean climatic data sets. Results from different data sets are intercompared and main common features identified. Monthly mean pressure observations from Isla de Pascua (27°10'S; 109°76'W) and Isla Juan Femándes (33°37*S; 78’52'W) are used to test some of these characteristics and to clarify others. Most significant properties of the location of maximum monthly mean pressure in Chile are then associated to PAC's position and pressure, allowing a linkage to be found between aspects oí Chilean climate and the identified PACs properties.. The PACs monthly mean latitude evolution role on these aspects of climate is highlighted.Asociación Argentina de Geofísicos y Geodesta

Variabilidad de los parámetros de radiopropagación asociada a cambios diarios en la ionósfera sobre Concepción, Chile

Se estudia la variabilidad de la concentración electrónica de la ianósfera sobre Concepción, Chile, y su efecto en la variabilidad de parámetros de radiopropagación. Se compara las distribuciones verticales de concentración electrónica, derivadas mediante la técnica de inversión de ionogramas, para el mediodía de unos pocos días de Mano de 1964, y que fueran publicados hace algún tiempo, con aquellas determinadas usando los modelos da Dudeney y de Bradley y Dudeney. Se encuentra que las distribuciones calculadas con las fórmulas de Dudeney se ajustan mejor a las obtenidas mediante inversión. Se encuentra que la variabilidad diaria de las distribuciones verticales modaladadas para el mediodía de la mayoría de los días de mano de 1964 es prácticamente independiente del modelo usado. La variabilidad cambia desde un 20% para alturas de la región E hasta alrededor de un 70% a 240 km. Se analisa el efecto de esta variabilidad diaria sobre parámetros de radiopropagación, usando resultados obtenidos con la técnica de trasudo de rayos, para sedales de 7.1 y y 14.2 MHs emitidas desde Concepción hacia el Norte y Este, con una serie de ángulos de elevación. Se incluye el efecto da la absorción radioeléctrica y del campo magnético. Los gráficos de distancia alcansada versus ángulo de elevación construidos muestran que los resultados asociados a las distribuciones verticales de Dudeney se ajustan mejor a los resultados correspondientes a la inversión de ionogramas que aquellos asociados a las distribuciones de Bradley y Dudeney. Se encuentra una variabilidad diaria del 100% para señales de 7.1 MHs y de 80% para señalas de 14.2 MHs que se propagan en modo E. Las variabilidades para el modo F son menores, sólo un 25% para 7.1 MHs y ángulo de elevación da 50° y 15% para 14.2 MHs y 30°.Ionospheric electron concentration variability over Concepción, Chile, and its effect on the variability of radiopropagation parameters are studied. Published vertical distributions of electron concentration far a few day of March 1964 at noon, derived using the ionogram inversion technique, are compared with those determined from Dudeney and Bradley and Dudeney models. Distributions computed using Dudeney's formulae are found to systematically better fit those related ionogram inversion. Day-to-day variability derived using modal vertical distributions far most day of March 1964 at noon is found to be independent of the model considered. It ranges from about 20% at E region heights to 70% at around 240 km. The effect of this day-to-day variability an radiopropagation parameters was analysed using ny—tracing results for lignait of 7.1 MHi and 14.2 MHi launched from Concepción towards the North and Eact, for a range of elevation angler. Geomagnetic field and radiowave absorption effects were included. Plots of range vanus elevation angle show that results associated to Dudeney's vertical distributions better fit those associated to ionogram inversion, than th* anti associated to Bradley and Dudeney distributions. E—mode range day-to-day variability amounts 100% for 7.1 MHi and 80% for 14.2 MHi. F—mode variabilities are smaller, being 25% for MHt signals launched at 50° and 15s for 14.2 MHi signals at 30s.Asociación Argentina de Geofísicos y Geodesta

Prediction of auroral absorption of high and medium frequency waves at oblique incidence

Imperial Users onl

Ionosonde measurements at Marsh, King George Island: First results

Routine ionospheric vertical-incidence soundings were started on 15 February 1986 at 1615 LT in Marsh using an IPS 42 model ionosonde coupled to Delta antennae. Sample ionograms are shown indicating the range of phenomena that can be observed. Conspicuous traces likely to be related to interference from a nearby ionosonde are discussed

Modelo empírico de un descriptor climático para la región central de Chile

Se analiza la evolución anual de la latitud y de la presión del lugar en Chile en que la presión media mensual es máxima, lugar que como se ha mostrado, tiene las propiedades de descriptor climático. Por medio de la técnica clásica de Fourier se determina las componentes anual y semlanual de las evoluciones de la latitud y la presión, y se encuentra que un modelo que incluya solo estas dos componentes reproduce muy bien las evoluciones observadas. Como era de esperar, las componentes anuales son las más importantes, tanto para la latitud como para la presión. Sin embargo, son las componentes semlanuales las que imprimen el rasgo característico a las evoluciones observadas, que consiste en un cambio mis rápido de la latitud de verano a invierno que el correspondiente de Invierno a verano, y en lo opuesto para la presión. Se asocia las componentes anuales a la evolución de la declinación solar y las sondan uales a la de la vaguada subantártlca. Se sugiere la posibilidad de separar laa contribuciones que tienen loa grandes centros de acción oceónlcos del Pacifico Sur en el descriptor climático.Observed annual evolutions of latitude and pressure of the location of maximum monthly-mean pressure along the Chilean coast are analysed, a location ha'dnq already known climatic descriptor properties. Annual and semiannual Fourier components of these evolutions are determlned, and It is shown that a model Including only these two components accounts for all main features of observed evolutions. As expected, annual components are the largest for both latitude and pressure. However, the semiannual components are the ones which give the observed evolutions their typical pattern, l.e. a faster latitude change from summer to winter compared to that from winter to summer, the oposite being the case for pressure changes. Annual components are associated to solar declina tlon changes and the semiannual ones to the trough of low pressure which surrounds Antarctica. It is suggested that contributions to the climatic descriptor associated to each of main Southern Pacific oceanl- action centres can be then Identified.Asociación Argentina de Geofísicos y Geodesta

Long-term trends in foF2: A comparison of various methods

Results of various authors on long-term trends in foF2, which is equivalent to the maximum electron density in the ionosphere, and their interpretation do not reveal a consistent pattern. Therefore, a joint analysis of one carefully selected dataset was performed by six teams, which used different approaches to trend determination. High-quality data of station Juliusruh (54.6ºN, 13.4ºE) for noon (average from 10 to 14 UT) were used for the period of two solar cycles from minimum to minimum (1976 ?1996). Juliusruh is relatively sensitive to geomagnetic activity as an almost subauroral station,which might play some role in interpretation of trend results.Various methods provide results,which differ to some extent, even when one co-author applies different methods.Another source of differences is application of various ways of removal (or at least large suppression) of the effect of solar (and geomagnetic)activity.Nevertheless .nally most teams obtained quite comparable results. Interpretation of the observed trends is not unique -co-authors consider either the long-term change in geomagnetic activity, or anthropogenic effects to be predominantly responsible for trends. There is some generally accepted output from the joint analysis.All trends are either negative or insignificant. Data corrections with sunspot number (R, F10.7 adjusted to the Sun -Earth distance, observed F10.7, adjusted E10.7 and observed E10.7 result in somewhat different trends; the observed F10.7 and E10.7 appear to be the best correcting factor. The trends in foF2 are very small, of the order of 0.01 MHz/year, much smaller than the solar cycle effect and, therefore, sensitive to the solar activity correction. The Juliusruh dip angle increased very little over the period 1976 -1996 and the possible impact of that increase on trends is negligibly small.Fil: Lastovicka, Jan. Institute Of Atmospheric Physics; República ChecaFil: Mikhailov, Andrei V.. Institute Of Terrestrial Magnetism; RusiaFil: Ulich, Thomas. Sodankyla Geophysical Observatory; FinlandiaFil: Bremer, Jurgen. Leibniz-institute Of Atmospheric Physics; AlemaniaFil: Elias, Ana Georgina. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; ArgentinaFil: Ortiz de Adler, Nieves del Carmen. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología; ArgentinaFil: Jara, V.. Universidad de Concepcion; ChileFil: Abarca del Rio, Rodrigo. Universidad de Concepcion; ChileFil: Foppiano, Alberto J.. Universidad de Concepcion; ChileFil: Ovalle, Elias. Universidad de Concepcion; ChileFil: Danilov, Andrei D.. Institute Of Applied Geophysics; Rusi

In haematopoietic SCT for acute leukemia TBI impacts on relapse but not survival: results of a multicentre observational study

The aim of this study was to determine whether parameters related to TBI impacted upon OS and relapse in patients with acute leukemia in CR who underwent haematopoietic SCT (HSCT) in 11 Italian Radiation Oncology Centres. Data were analysed from 507 patients (313 males; 194 females; median age 15 years; 318 with ALL; 188 with AML; 1 case not recorded). Besides 128 autologous transplants, donors included 192 matched siblings, 74 mismatched family members and 113 unrelated individuals. Autologous and allogeneic transplants were analysed separately. Median follow-up was 40.1 months. TBI schedules and HSCT type were closely related. Uni- and multi-variate analyses showed no parameter was significant for OS or relapse in autologous transplantation. Multivariate analysis showed type of transplant and disease impacted significantly on OS in allogeneic transplantation. Disease, GVHD and TBI dose were risk factors for relapse. This analysis illustrates that Italian Transplant Centre use of TBI is in line with international practice. Most Centres adopted a hyperfractionated schedule that is used worldwide (12 Gy in six fractions over 3 days), which appears to have become standard. TBI doses impacted significantly upon relapse rates

In haematopoietic SCT for acute leukemia TBI impacts on relapse but not survival: results of a multicentre observational study

The aim of this study was to determine whether parameters related to TBI impacted upon OS and relapse in patients with acute leukemia in CR who underwent haematopoietic SCT (HSCT) in 11 Italian Radiation Oncology Centres. Data were analysed from 507 patients (313 males; 194 females; median age 15 years; 318 with ALL; 188 with AML; 1 case not recorded). Besides 128 autologous transplants, donors included 192 matched siblings, 74 mismatched family members and 113 unrelated individuals. Autologous and allogeneic transplants were analysed separately. Median follow-up was 40.1 months. TBI schedules and HSCT type were closely related. Uni- and multi-variate analyses showed no parameter was significant for OS or relapse in autologous transplantation. Multivariate analysis showed type of transplant and disease impacted significantly on OS in allogeneic transplantation. Disease, GVHD and TBI dose were risk factors for relapse. This analysis illustrates that Italian Transplant Centre use of TBI is in line with international practice. Most Centres adopted a hyperfractionated schedule that is used worldwide (12 Gy in six fractions over 3 days), which appears to have become standard. TBI doses impacted significantly upon relapse rates