64 research outputs found
The anisotropy of galactic cosmic rays as a product of stochastic supernova explosions
We study the effect of the stochastic character of supernova explosions on the anisotropy of galactic cosmic rays below the knee. We conclude that if the bulk of cosmic rays are produced in supernova explosions the observed small and nearly energy independent amplitude of the anisotropy and its phase are to the large extent determined by the history of these explosions in the vicinity of the solar system, namely by the location and the age of the supernova remnants, within a few kpc, which give the highest contribution to the total intensity at the present epoch. Among the most important factors which result in the small magnitude and the energy independence of the anisotropy amplitude are the mixed primary mass composition, the effect of the single source and the galactic Halo. Special attention is given to the phase of the anisotropy. It is shown that the excessive cosmic ray flux from the outer Galaxy can be due to the location of the solar system at the inner edge of the Orion arm which has the enhanced density and rate of supernova explosions
How Should We Modify the High Energy Interaction Models ?
An analysis has been made of the present situation with respect to the high
energy hadron-nucleus and nucleus-nucleus interaction models as applied to
cosmic rays. As is already known, there are inconsistencies in the
interpretation of experimental data on the primary mass composition, which
appear when different EAS components are used for the analyses, even for the
same experiment. In the absence of obvious experimental defects, there is a
clear need for an improvement to the existing models; we argue that the most
promising way is to enlist two effects which should be present in nucleus-
nucleus collisions but have not been allowed for before. These are: a few
percent energy transfer into the EAS electromagnetic component due to electron-
positron pair production or electromagnetic radiation of the quark-gluon plasma
and a small slow-down of the cascading process in its initial stages associated
with the extended lifetime of excited nuclear fragments. The latter process
displaces the shower maximum deeper into the atmosphere.Comment: 4 pages, 3 figures, talk presented at XII International Symposium on
Very High Energy Cosmic Ray Interactions, CERN, Geneva, 15-19 July 2002, to
be published in Nucl.Phys.B (Proc. Suppl.
Fine structure in the gamma-ray sky and the origin of UHECR
The EGRET results for gamma ray intensities in and near the Galactic Plane
have been analysed in some detail. Attention has been concentrated on energies
above 1 GeV and the individual intensities in a longitude bin have
been determined and compared with the large scale mean found from a nine-degree
polynomial fit. Comparison has been made of the observed standard deviation for
the ratio of these intensities with that expected from variants of our model.
The basic model adopts cosmic ray origin from supernova remnants, the particles
then diffusing through the Galaxy with our usual `anomalous diffusion'. The
variants involve the clustering of SN, a frequency distribution for supernova
explosion energies, and 'normal', rather than 'anomalous' diffusion.
It is found that for supernovae of unique energy, and our usual anomalous
diffusion, clustering is necessary, particularly in the Inner Galaxy. An
alternative, and preferred, situation is to adopt the model with a frequency
distribution of supernova energies. The results for the Outer Galaxy are such
that no clustering is required.
If their explosion energies are distributed then supernovae can be the origin
of UHECR.Comment: 8 pages, 5 figures and 1 table, to appear in the proceedings of the
CRIS2006 symposium, Catania, Italy, May-June 200
The Anatomy of the Knee and Gamma-Families
It is shown that the fine stucture of the cosmic ray energy spectrum in the
knee region, if explained by the Single Source Model (SSM), can, in principle,
be clearly revealed and magnified in the size spectrum of extensive air showers
(EAS) associated with gamma families. Existing experimental data on EAS at
mountain level give support to this hypothesis.Comment: 4 pages, 3 figures, to appear in the Proceedings of 14th
International Symposium on Very High Energy Cosmic Ray Interactions, Weihai,
China, 15-22.08.06, Nucl.Phys.B (Proc.Suppl.), 200
Spectral Features and Masses in the PeV Region
An analysis is made of the masses and spectral features for cosmic rays in
the PeV region, insofar as they have a bearing on the problem of the
interaction of cosmic ray particles. In our Single Source Model we identified
two 'peaks' seen in a summary of the world's data on primary spectra, and
claimed that they are probably due to oxygen and iron nuclei from a local,
recent supernova. In the present work we examine other possible mass
assignments. We conclude that of the other possibilities only Helium and Oxygen
(instead of O and Fe) has much chance of success; the original suggestion is
still preferred, however. Concerning our location with respect to the SNR
shell, the analysis suggests that we are close to it - probably just inside.Comment: 4 pages, 2 figures, talk presented at XII Inrternational Symposium on
Very High Energy Cosmic Ray Interactions, CERN, Geneva, 15-19 July 2002, to
be published in Nucl.Phys.B (Proc.Suppl.
Clouds, solar irradiance and mean surface temperature over the last century
The inter-relation of clouds, solar irradiance and surface temperature is
complex and subject to different interpretations. Here, we continue our recent
work, which related mainly to the period from 1960 to the present, back to 1900
with further, but less detailed, analysis of the last 1000 years. The last 20
years is examined especially. Attention is given to the mean surface
temperature, solar irradiance correlation, which appears to be present (with
decadal smoothing) with a 22-year period; it is stronger than the 11-year cycle
correlation with one year resolution. UV in the solar radiation is a likely
cause. Cloud data are taken from synoptic observations back to 1952 and, again,
there appears to be a correlation - with opposite phase for high and low clouds
- at the 20-30y level. Particular attention is devoted to answering the
question, 'what fraction of the observed increase in mean Global temperature
(~0.7^oC) can be attributed to solar, as distinct from man-made, effects?' We
conclude that a best estimate is 'essentially' all from 1900 to 1956 and <14%
from 1956 to the present.Comment: 10 pages, 6 figures, accepted by Journal of Atmospheric and
Solar-Terrestrial Physic
The contribution of cosmic rays to global warming
A search has been made for a contribution of the changing cosmic ray
intensity to the global warming observed in the last century. The cosmic ray
intensity shows a strong 11 year cycle due to solar modulation and the overall
rate has decreased since 1900. These changes in cosmic ray intensity are
compared to those of the mean global surface temperature to attempt to quantify
any link between the two. It is shown that, if such a link exists, the changing
cosmic ray intensity contributes less than 8% to the increase in the mean
global surface temperature observed since 1900.Comment: 12 pages, 5 figures, accepted for publication in J. of Atmospheric
and Solar-Terrestrial physic
Models for the Origin of the Knee in the Cosmic-Ray Spectrum
A sudden steepening of the cosmic-ray energy spectrum (the knee) is observed
at an energy of about 3 PeV (1 PeV = eV). The experimental study of
the PeV cosmic rays has intensified greatly during the last 3 years. The recent
results on extensive air showers allow us to conclude that: a) the knee has an
astrophysical origin; b) the `sharpness' and the fine structure of the knee
rule out `Galactic Modulation' as the origin of the knee; c) most likely the
knee is the result of the explosion of a single, recent, nearby supernova.Comment: 10 pages, 6 figures, submitted to Advances in Space Researc
On the correlation between cosmic ray intensity and cloud cover
Various aspects of the connection between cloud cover (CC) and cosmic rays
(CR) are analysed. Many features of this connection indicate that there is no
direct causal connection between low cloud cover (LCC) and CR in spite of the
evident long-term correlation between them. However, most of these features are
indirect. If only some part of the LCC is connected and varies with CR, then
its value, obtained from the joint analysis of their 11-year variations, and
averaged over the globe, should be most likely less than 20%.
The most significant argument against a causal connection of CR and LCC is
the anticorrelation between LCC and the medium cloud cover (MCC). The scenario
of the parallel influence of the solar activity on the global temperature and
CC on one side and CR on the other, which can lead to the observed
correlations, is discussed and advocated.Comment: 30 pages, 10 figures, accepted for publication in Journal of
Atmospheric and Solar-Terrestrial Physics, acknowledgements replace
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