102 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
A Model of the Influence of Neutral Air Dynamics on the Seasonal Variation in the Low Ionosphere
Recently it has become clear that the phenomena in the ionospheric D-region are determined to a great extent by dynamical processes in the strato-mesosphere D-region. In this respect much attention is paid to the study of the winter anomaly (WA) phenomenon on medium and short radiowaves, in which the meteorological character of the lower ionosphere is most prominent. Significant experimental data about the variations of the electron concentration, N, ion composition, temperature and dynamic regime during WA permit a better understanding of the character of the physical processes in the middle atmosphere. The influence of the neutral wind on the seasonal variation of the electron concentration N for the altitude interval 90 or = z or = 120 km, where the ratio upsilon sub in/omega sub i, of the ion-neutral collision frequency, upsilon sub in and the ion gyrofrequency, omega sub i decreases from 40 to 1 was evaluated. CIRA-72 is used as a model of the zonal wind
Explanation of the Normal Winter Anomaly from the Seasonal Variation of Short Wave Absorption
The frequency dependence of the winter anomaly (WA) of radio wave absorption indicates the altitude range where the considered seasonal variation of absorption, L, takes place: 75-95 km. In this height region considerable seasonal variations of ionic composition and effective recombination coefficient, alpha sub e, exist, which can cause seasonal variations of electron concentration, N, and absorption, L. An attempt to render a qualitative estimation of the normal WA, i.e., the increased ratio of winter over summer absorption, L sub w/L sub s, at medium latitudes 40 deg and 50 deg, for solar zenith angles CHi = 60 deg and 75 deg is made. This is compared with existing experimental data
3-D model for cosmic ray planetary ionisation in the middle atmosphere
International audienceA 3-D planetary model of the cosmic ray electron production rate q(h) (cm-3 s-1) has been developed for the strato-mesosphere and lower thermosphere (altitude range 30-100 km) with a 10-km step. The spectrum of the primary cosmic rays is modelled by an analytical expression using input data from the CREME96 model. An isotropic penetration of the cosmic rays from the upper hemisphere is assumed in the model and a spherical shape of the Earth's atmosphere is taken into account. The longitudinal effect of ionisation from cosmic rays in the mesosphere and lower thermosphere is calculated. A graphical presentation of the computational results is given for 50 and 90 km at 0°, 40°, 50° and 70° N, S latitudes and all longitudes with a step of 30°. The results of this paper provide a basis for a quantitative understanding of the energetic processes of the middle atmosphere and mechanisms affecting the thermodynamical balance of the Earth's atmosphere
The Effect of Tumbling, Sodium Chloride and Polyphosphates on the Microstructure and Appearance of Whole-Muscle Processed Meats
The properties of a whole-muscle processed meat were determined. The complex action of socium chloride, polyphosphates and mechanical agitation caused extraction of myofibrillar protein, swelling of fibers and loss of cross-strations. A new functional ability was found for the extracted proteins to form a fine cover or membrane on the surface of the whole muscle during cooking. These changes produced a product with improved cooking yield and color appearance
Testing the proposed link between cosmic rays and cloud cover
A decrease in the globally averaged low level cloud cover, deduced from the
ISCCP infra red data, as the cosmic ray intensity decreased during the solar
cycle 22 was observed by two groups. The groups went on to hypothesise that the
decrease in ionization due to cosmic rays causes the decrease in cloud cover,
thereby explaining a large part of the presently observed global warming. We
have examined this hypothesis to look for evidence to corroborate it. None has
been found and so our conclusions are to doubt it. From the absence of
corroborative evidence, we estimate that less than 23%, at the 95% confidence
level, of the 11-year cycle change in the globally averaged cloud cover
observed in solar cycle 22 is due to the change in the rate of ionization from
the solar modulation of cosmic rays
Progress in space weather modeling in an operational environment
This paper aims at providing an overview of latest advances in space weather modeling in an operational environment in Europe,
including both the introduction of new models and improvements to existing codes and algorithms that address the broad range of space weather’s prediction requirements from the Sun to the Earth. For each case, we consider the model’s input data, the output
parameters, products or services, its operational status, and whether it is supported by validation results, in order to build a solid basis for future developments. This work is the output of the Sub Group 1.3 ‘‘Improvement of operational models’’ of the European Cooperation in Science and Technology (COST) Action ES0803 ‘‘Developing Space Weather Products and services in Europe’’ and therefore this review focuses on the progress achieved by European research teams involved in the action
Long term time variability of cosmic rays and possible relevance to the development of life on Earth
An analysis is made of the manner in which the cosmic ray intensity at Earth
has varied over its existence and its possible relevance to both the origin and
the evolution of life. Much of the analysis relates to the 'high energy' cosmic
rays () and their variability due to the changing
proximity of the solar system to supernova remnants which are generally
believed to be responsible for most cosmic rays up to PeV energies. It is
pointed out that, on a statistical basis, there will have been considerable
variations in the likely 100 My between the Earth's biosphere reaching
reasonable stability and the onset of very elementary life. Interestingly,
there is the increasingly strong possibility that PeV cosmic rays are
responsible for the initiation of terrestrial lightning strokes and the
possibility arises of considerable increases in the frequency of lightnings and
thereby the formation of some of the complex molecules which are the 'building
blocks of life'. Attention is also given to the well known generation of the
oxides of nitrogen by lightning strokes which are poisonous to animal life but
helpful to plant growth; here, too, the violent swings of cosmic ray
intensities may have had relevance to evolutionary changes. A particular
variant of the cosmic ray acceleration model, put forward by us, predicts an
increase in lightning rate in the past and this has been sought in Korean
historical records. Finally, the time dependence of the overall cosmic ray
intensity, which manifests itself mainly at sub-10 GeV energies, has been
examined. The relevance of cosmic rays to the 'global electrical circuit'
points to the importance of this concept.Comment: 18 pages, 5 figures, accepted by 'Surveys in Geophysics
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