http://hdl.handle.net/2122/89 Search the Channel search http://www.earth-prints.org/simple-search http://hdl.handle.net/2122/4165 Title: EFFECTS OF ENERGETIC SOLAR PARTICLES ON OZONE AND MINOR ATMOSPHERIC COMPONENTS INSIDE THE POLAR REGIONS <br/> <br/>Authors: Damiani, A.; INAF-IFSI <br/> <br/>Abstract: Solar activity influences the Earth’s environment, in particular the atmospheric ozone, by the direct output of the e.m. radiation or through the variability of the incoming cosmic ray flux (solar and galactic particles). Especially energetic particles, arising from huge explosions on the Sun’s surface, travel in the interplanetary medium and, if the circumstances were favorable, they could enter the terrestrial atmosphere (driven by the geomagnetic field lines of our planet) and reach the polar cap regions (geomagnetic latitude > 60°). There, they provide additional external energy and are able to produce ionizations, dissociations, dissociative ionizations and excitations phenomena by interacting with the minor constituents. The induced changes are not confined to the ion chemistry but also to the neutral components. In this way a rise of the concentration of HOx and NOx species and the triggering of catalytic cycles which lead to short (hours) and medium (days) term ozone destruction occur. Finally, also no-reactive reservoir species (e.g., HNO3, HCl, HOCl) are involved in these processes and endure large variations. The present thesis highlights the chemical variability of the middle atmosphere during and after some Solar Energetic Particle (SEP) events recorded during the current solar cycle. Special attention has been paid to the relationship between ozone and HOx data (retrieved from the Microwave Limb Sounder of EOS AURA satellite) for four events referred to 2005. The HOx data, recorded for the first time during the intense ionization caused by the SEP flux, have pointed out some features related to these phenomena not wholly captured by the current theoretical models. In addition, they have highlighted that the HOx rise is able to destroy the so-called third ozone peak at the polar latitudes of the winter hemisphere and it occurs also during medium intensity events. Besides, the analyses of January 2005 SEP events have shown that the changes on the hydrogen species leaded to variability in the concentration and partitioning of chlorine family, not discernible in the summer hemisphere. Further, the use of data coming from the HALOE instrument, referred to SEP events occurred in July 2000 and April 2002, has in short confirmed past experimental results. Finally, the study of a little SEP event occurred during May 2003 has pointed out that SEP events are not the unique ionization source inside the polar latitudes during the winter. Wed, 28 Nov 2007 22:58:59 GMT http://hdl.handle.net/2122/3982 Title: Space weather and RF communications: Monitoring and modelling <br/> <br/>Authors: Cander, Lj. R.; Rutherford Appleton Laboratory, Space Science & Technology Department, Radio Communications Research Unit, Chilton, Didcot, Oxon OX11 0QX, UK; Zolesi, B.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia <br/> <br/>Abstract: At the beginning of the new millennium, ionospheric physics and its application in new technologies are at a point of significant change and new development. Ionospheric studies in the past found application in the traditional areas of broadcast and terrestrial radio communications. It has become clear, in recent years, that an understanding of the ionosphere, as a part of the upper atmosphere, is central to the design of many modern communication, navigation and positioning systems. An important additional role has also been recognized in the areas of space weather science and services. This issue of the Journal of Atmospheric and Solar-Terrestrial Physics collects selected contributions presented at the Solar-Terrestrial Sciences session ST14 on "Space weather and RF communications: monitoring and modelling" held during the first General Assembly of the European Geosciences Union (Nice, France, 25–30 April 2004). <br/> <br/>Description: Preface to Journal of Atmospheric and Solar-Terrestrial Physics 67 (2005) Fri, 29 Jul 2005 22:58:59 GMT http://hdl.handle.net/2122/2796 Title: Degassing of gaseous (elemental and reactive) and particulate mercury from Mount Etna volcano (Southern Italy) <br/> <br/>Authors: Bagnato, E.; Università di Palermo, Dipartimento CFTA; Aiuppa, A.; Università di Palermo, Dipartimento CFTA; Parello, F.; Università di Palermo, Dipartimento CFTA; Calabrese, S.; Università di Palermo, Dipartimento CFTA; D'Alessandro, W.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Mather, T. A.; Department of Earth Sciences, University of Oxford, UK; McGonigle, A. J. S.; Department of Geography, University of Sheffield, UK; Pyle, D. M.; Department of Earth Sciences, University of Oxford, UK; Wängberg, I.; IVL-Swedish Environmental Research Institute, Göteborg, Sweden <br/> <br/>Abstract: There is an urgent need to better constrain the global rates of mercury degassing from natural sources, including active volcanoes. Hitherto, estimates of volcanic fluxes have been limited by the poorly-determined speciation of Hg in volcanic emissions. Here, we present a systematic characterisation of mercury partitioning between gaseous (Hg(g)) and particulate (Hg(p)) forms in the volcanic plume of Mount Etna, the largest open-vent passively degassing volcano on Earth. We demonstrate that mercury transport is predominantly in the gas-phase, with a mean Hg(p)/Hg(g) ratio of ∼0.01 by mass. We also present the first simultaneous measurement of divalent gaseous mercury (HgII(g)) and total gaseous mercury (Hg(g)) in a volcanic plume, which suggests that Hg0(g) is the prevalent form of mercury in this context. These data are supported by the results of model simulations, carried out with HSC thermodynamic software. Based on a mean ‘bulk plume’ Hg/SO2 mass ratio of 8.7×10-6, and a contemporaneous volcanic SO2 flux of 0.8 Mt·yr-1, we estimate an Hg emission rate from Mt. Etna during passive degassing of 5.4 t·y-1 (range, 1.1-10 t·y-1). This corresponds to ~0.6% of global volcanic Hg emissions, and about 5% of Hg released from industrial activities in the Mediterranean area. Mon, 29 Oct 2007 22:58:59 GMT http://hdl.handle.net/2122/2583 Title: Aspects of stratospheric long-term changes induced by ozone depletion <br/> <br/>Authors: Cagnazzo, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Claud, C.; Laboratoire de Me´ te´ orologie Dynamique du CNRS, Institut Pierre et Simon Laplace (IPSL), Ecole Polytechnique; Hare, S.; Department of Meteorology, University of Reading, Earley Gate <br/> <br/>Abstract: The effect of the stratospheric ozone depletion on the thermal and dynamical structure of the middle atmosphere is assessed using two 5-member ensembles of transient GCM simulations; one including linear trends in ozone, the other not, for the 1980–1999 period. Simulated temperatures and observations are in good agreement in terms of mean values, autocorrelations and cross correlations. Annual-mean and seasonal temperature trends have been calculated using the same statistical analysis. Simulations show that ozone trends are responsible for reduced wave activity in the Arctic lower stratosphere in February and March, confirming both the role of dynamics in controlling March temperatures and a recently proposed mechanism whereby Arctic ozone depletion causes the reduction in wave activity entering the lower stratosphere. Changes in wave activity are consistent with an intensification of the polar vortex at the time of ozone depletion and with a weakened Brewer–Dobson circulation: A decrease of the dynamical warming/cooling associated with the descending/ascending branch of the wintertime mean residual circulation at high/low latitudes has been obtained through the analysis of temperature observations (1980–1999). Ozone is responsible of about one third of the decrease of this dynamical cooling at high latitudes. An increase in the residual mean circulation is seen in the observations for the 1965–1980 period. Sat, 29 Oct 2005 22:58:59 GMT