5,540 research outputs found
Hadron Generator and Atmospheric Seasonal Variation Influence on Cosmic Ray Ionization computed with CORSIKA Code
Recently an essential progress in development of physical models for cosmic
ray induced ionization in the atmosphere is achieved. Basically, the models are
full target, i.e. based on Monte Carlo simulation of an
electromagnetic-muon-nucleon cascade in the atmosphere. In general, the
contribution of proton nuclei in those models is highlighted, i.e. primary
cosmic ray -particles and heavy nuclei are neglected or scaled to
protons. The development of cosmic ray induced atmospheric cascade is sensitive
to the energy and mass of the primary cosmic ray particle. The largest
uncertainties in Monte Carlo simulations of a cascade in the Earth atmosphere
are due to assumed hadron interaction models, the so-called hadron generators.
In the work presented here we compare the ionization yield functions for
primary cosmic ray nuclei, such as protons, -particles, Oxygen and Iron
nuclei, assuming different hadron interaction models. The computations are
fulfilled with the CORSIKA 6.9 code using GHEISHA 2002, FLUKA 2011, UrQMD
hadron generators for energy below 80 GeV/nucleon and QGSJET II for energy
above 80 GeV/nucleon. The observed difference between hadron generators is
widely discussed. The influence of different atmospheric parametrizations,
namely US standard atmosphere, US standard atmosphere winter and summer
profiles on ion production rate is studied. Assuming realistic primary cosmic
ray mass composition, the ion production rate is obtained at several rigidity
cut-offs - from 1 GV (high latitudes) to 15 GV (equatorial latitudes) using
various hadron generators. The computations are compared with experimental
data. A conclusion concerning the consistency of the hadron generators is
stated.Comment: 24 pages, 11 figures, extended version of paper accpted for
publication in JAST
Big Bang Nucleosynthesis and Cosmological Constraints on Neutrino Oscillation Parameters
We present a review of cosmological nucleosynthesis (CN) with neutrino
oscillations, discussing the different effects of oscillations on CN, namely:
increase of the effective degrees of freedom during CN, spectrum distortion of
the oscillating neutrinos, neutrino number density depletion, and growth of
neutrino-antineutrino asymmetry due to active-sterile oscillations. We discuss
the importance of these effects for the primordial yield of helium-4.
Primordially produced He-4 value is obtained in a selfconsistent study of the
nucleons and the oscillating neutrinos. The effects of spectrum distortion,
depletion and neutrino-antineutrino asymmetry growth on helium-4 production are
explicitly calculated.
An update of the cosmological constraints on active-sterile neutrino
oscillations parameters is presented, giving the values: delta m^2 sin^8 (2
theta) 0, and |delta m^2| < 8.2 x 10^{-10}
eV^2 at large mixing angles for delta m^2 < 0. According to these constraints,
besides the active-sterile LMA solution, also the active-sterile LOW solution
to the solar neutrino problem is almost totally excluded.Comment: Extended and updated version of the invited talk, presented at the
International Conference "Hot Points in Astrophysics", held in JINR, Dubna,
Russia, August 22-26, 2000. An update of the cosmological constraints on
active-sterile neutrino oscillation parameters is presented (Fig.2 added
A new model of cosmogenic production of radiocarbon 14C in the atmosphere
We present the results of full new calculation of radiocarbon 14C production
in the Earth atmosphere, using a numerical Monte-Carlo model. We provide, for
the first time, a tabulated 14C yield function for the energy of primary cosmic
ray particles ranging from 0.1 to 1000 GeV/nucleon. We have calculated the
global production rate of 14C, which is 1.64 and 1.88 atoms/cm2/s for the
modern time and for the pre-industrial epoch, respectively. This is close to
the values obtained from the carbon cycle reservoir inventory. We argue that
earlier models overestimated the global 14C production rate because of outdated
spectra of cosmic ray heavier nuclei. The mean contribution of solar energetic
particles to the global 14C is calculated as about 0.25% for the modern epoch.
Our model provides a new tool to calculate the 14C production in the Earth's
atmosphere, which can be applied, e.g., to reconstructions of solar activity in
the past.Comment: Published in EPSL, 337, 114, 201
Seasonal distributions of fine aerosol sulfate in the North American Arctic basin during TOPSE
We used the mist chamber/ion chromatography technique to quantify fine aerosol SO4=(\u3c2.7 Όm) in the Arctic during the Tropospheric Ozone Production about the Spring Equinox Experiment (TOPSE) with about 2.5 min time resolution. Our effective sample area ranged from 50° to 86°N and 53° to 100°W. The seasonal evolution of fine aerosol sulfate in the Arctic troposphere during TOPSE was consistent with the phenomenon of Arctic haze. Arctic haze has been attributed to pollution from sources in the Arctic and pollution transported meridionally along stable isentropes into the Arctic in geographically broad but vertically narrow bands. These layers became more prevalent at higher altitudes as the season progressed toward summer, and the relevant isentropes are not held so close to the surface. Mean fine particle SO4= mixing ratios during TOPSE in February below 1000 m were elevated (112 pptv) and highly variable (between 28 and 290 pptv) but were significantly lower at higher altitudes (about 40 pptv). As the season progressed, elevated mixing ratios and higher variability were observed at higher altitudes, up to 7 km. In May, mixing ratios at the lowest altitudes declined but still remained higher than in February at all altitudes. The high variability in our measurements likely reflects the vertical heterogeneity of the wintertime Arctic atmosphere as the airborne sampling platform passed in and out of these layers. It is presumed that mixing ratios and variability will continue to decline at all altitudes into the summer as wet deposition processes become important in removing aerosol SO4= from the troposphere
A Comprehensive Emission Inventory of Bbiogenic Volatile Organic Compounds in Europe: Improved Seasonality and Land-cover
Biogenic volatile organic compounds (BVOC) emitted from vegetation are important for the formation of secondary pollutants such as ozone and secondary organic aerosols (SOA) in the atmosphere. Therefore, BVOC emission are an important input for air quality models. To model these emissions with high spatial resolution, the accuracy of the underlying vegetation inventory is crucial. We present a BVOC emission model that accommodates different vegetation inventories and uses satellite-based measurements of greenness instead of pre-defined vegetation periods. This approach to seasonality implicitly treats effects caused by water or nutrient availability, altitude and latitude on a plant stand. Additionally, we test the influence of proposed seasonal variability in enzyme activity on BVOC emissions. In its present setup, the emission model calculates hourly emissions of isoprene, monoterpenes, sesquiterpenes and the oxygenated volatile organic compounds (OVOC) methanol, formaldehyde, formic acid, ethanol, acetaldehyde, acetone and acetic acid. In this study, emissions based on three different vegetation inventories are compared with each other and diurnal and seasonal variations in Europe are investigated for the year 2006. Two of these vegetation inventories require information on tree-cover as an input. We compare three different land-cover inventories (USGS GLCC, GLC2000 and Globcover 2.2) with respect to tree-cover. The often-used USGS GLCC land-cover inventory leads to a severe reduction of BVOC emissions due to a potential miss-attribution of broad-leaved trees and reduced tree-cover compared to the two other land-cover inventories. To account for uncertainties in the land-cover classification, we introduce land-cover correction factors for each relevant land-use category to adjust the tree-cover. The results are very sensitive to these factors within the plausible range. For June 2006, total monthly BVOC emissions decreased up to â27% with minimal and increased up to +71% with maximal factors, while in January 2006, the changes in monthly BVOC emissions were â54 and +56% with minimal and maximal factors, respectively. The new seasonality approach leads to a reduction in the annual emissions compared with non-adjusted data. The strongest reduction occurs in OVOC (up to â32 %), the weakest in isoprene (as little as â19 %). If also enzyme seasonality is taken into account, however, isoprene reacts with the steepest decrease of annual emissions, which are reduced by â44% to â49 %, annual emissions of monoterpenes reduce between â30 and â35 %. The sensitivity of the model to changes in temperature depends on the climatic zone but not on the vegetation inventory. The sensitivity is higher for temperature increases of 3K (+31% to +64 %) than decreases by the same amount (â20 to â35 %). The climatic zones âCold except summerâ and âaridâ are most sensitive to temperature changes in January for isoprene and monoterpenes, respectively, while in June, âpolarâ is most sensitive to temperature for both isoprene and monoterpenes. Our model predicts the oxygenated volatile organic compounds to be the most abundant fraction of the annual European emissions (3571â5328 Gg yrâ1), followed by monoterpenes (2964â4124 Gg yrâ1), isoprene (1450â2650 Gg yrâ1) and sesquiterpenes (150â257 Gg yrâ1). We find regions with high isoprene emissions (most notably the Iberian Peninsula), but overall, oxygenated VOC dominate with 43â45% (depending on the vegetation inventory) contribution to the total annual BVOC emissions in Europe. Isoprene contributes between 18â21 %, monoterpenes 33â36% and sesquiterpenes contribute 1â2 %.We compare the concentrations of biogenic species simulated by an air quality model with measurements of isoprene and monoterpenes in Hohenpeissenberg (Germany) for both summer and winter. The agreement between observed and modelled concentrations is better in summer than in winter. This can partly be explained with the difficulty to model weather conditions in winter accurately, but also with the increased anthropogenic influence on the concentrations of BVOC compounds in winter. Our results suggest that land-cover inventories used to derive tree-cover must be chosen with care. Also, uncertainties in the classification of land-cover pixels must be taken into account and remain high. This problem must be addressed together with the remote sensing community. Our new approach using a greenness index for addressing seasonality of vegetation can be implemented easily in existing models. The importance of OVOC for air quality should be more deeply addressed by future studies, especially in smog chambers. Also, the fate of BVOC from the dominant region of the Iberian Peninsula should be studied more in detail
Environmental, human health and socio-economic effects of cement powders: The multicriteria analysis as decisional methodology
The attention to sustainability-related issues has grown fast in recent decades. The experience gained with these themes reveals the importance of considering this topic in the construction industry, which represents an important sector throughout the world. This work consists on conducting a multicriteria analysis of four cement powders, with the objective of calculating and analysing the environmental, human health and socio-economic effects of their production processes. The economic, technical, environmental and safety performances of the examined powders result from official, both internal and public, documents prepared by the producers. The Analytic Hierarchy Process permitted to consider several indicators (i.e., environmental, human health related and socio-economic parameters) and to conduct comprehensive and unbiased analyses which gave the best, most sustainable cement powder. As assumed in this study, the contribution of each considered parameter to the overall sustainability has a different incidence, therefore the procedure could be used to support on-going sustainability efforts under different conditions. The results also prove that it is not appropriate to regard only one parameter to identify the âbestâ cement powder, but several impact categories should be considered and analysed if there is an interest for pursuing different, often conflicting interests
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