Publications (71)59.02 Total impact
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Article: Cosmic ray anisotropies to 5 PeV
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ABSTRACT: Several large cosmic ray (CR) detectors have recently provided data on the arrival directions of CR, which taken together with previous data recorded over many decades allow the amplitgude and phase of the first harmonic to be derived with reasonable precision and up to higher energies. We find a high degree of consistency amongst the various measurements. The new data indicate that at an energy above ~0.1 PeV a change of the CR anisotropy sets in. The amplitude of the first harmonic, which rises to 3 TeV, then diminishes and begins to rise again. The direction of the phase also changes to the opposite one. A measure of understanding follows from the use of two-dimensional maps of CR excesses over the mean background. When the energy of CR approaches the PeV region, the excess of CR moves from the Galactic Anti-Centre to the opposite direction of the Galactic Centre. The possible role of such potential CR sources as the supernovae Monogem Ring and Vela, which could help to explain some of the observed results, is discussed.03/2013; -
Article: On the nature of the correlation between cosmic-ray intensity and cloud cover
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ABSTRACT: Various aspects of the connection between low cloud cover (LCC) and cosmic rays (CRs) are considered. Most features of this connection point to the absence of substantial causal relationship between LCC and CRs. Even on the assumption that some LCC fraction is related to CR intensity and varies with it, its most likely value is about 2% (although, within two standard deviations it can be as high as 20%). The most serious argument against the causal relationship between CRs and LCC is the existence of negative correlation between low and medium cloud cover (MCC). The scenario of simultaneous influence of solar activity on CRs and cloud cover is discussed, which might lead to the observed correlations.Bulletin of the Russian Academy of Sciences Physics 05/2012; 73(3):390-393. -
Article: Global Cloud Cover and the Earth’s Mean Surface Temperature
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ABSTRACT: The well-known 11-year cycle in low cloud cover amount for Solar Cycle Number 22 and the trend with time for Solar Cycle Number 23 are interpreted as being due to similar changes, but of opposite phase, in the mean global surface temperature of the Earth. An analysis of cloud amounts in two higher altitude bands shows that they, and the surface temperature, are roughly in phase with each other. The suggested mechanism to explain this result is that a warming of the Earth’s surface causes low clouds to rise and to be reclassified in the next upper category. The energetics of the process are shown to be satisfactory for this to be the correct explanation. KeywordsGlobal cloud cover-Surface temperature-EnergeticsSurveys in Geophysics 04/2012; 31(4):399-408. · 3.09 Impact Factor -
Article: Fine structure in the cosmic ray spectrum: Further analysis and the next step
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ABSTRACT: An analysis is made of the fine structure in the cosmic ray energy spectrum: new facets of present observations and their interpretation and the next step. It is argued that less than about 10% of the intensity of the helium `peak' at the knee at $\simeq 5PeV$ is due to just a few sources (SNR) other than the single source. The apparent concavity in the rigidity spectra of protons and helium nuclei which have maximum curvature at about 200 GV is confirmed by a joint analysis of the PAMELA, CREAM and ATIC experiments. The spectra of heavier nuclei also show remarkable structure in the form of `ankles' at several hundred GeV/nucleon. Possible mechanisms are discussed. The search for `pulsar peaks' has not yet proved successful.11/2011; -
Article: Fluctuations in some climate parameters
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ABSTRACT: There is argument as to the extent to which there has been an increase over the past few decades in the frequency of the extremes of climatic parameters, such as temperature, storminess, precipitation, etc, an obvious point being that Global Warming might be responsible. Here we report results on those parameters of which we have had experience during the last few years: Global surface temperature, Cloud Cover and the MODIS Liquid Cloud Fraction. In no case we have found indications that fluctuations of these parameters have increased with time.04/2011; -
Article: Do we see an'Iron Peak'?
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ABSTRACT: An update of the fine structure in the cosmic ray (CR) energy spectrum at PeV and tens of PeV energies is presented. The existence of the bump at 50–80 PeV found in the GAMMA experiment is supported by 9 other experi-ments. If it is a real feature it might indicate the existence of the so called 'Iron Peak', i.e. the end of the contribution of a 'Single Source' to the background of CR from other sources. We argue that the new feature in the fine structure of the CR energy spectrum makes the evidence in favour of the pres-ence of a 'Single Source' stronger than before.Astrophys. Space Sci. Trans. 01/2011; 7:145-150. -
Article: Clouds, solar irradiance and mean surface temperature over the last century
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ABSTRACT: 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 Physics03/2010; -
Article: Long term time variability of cosmic rays and possible relevance to the development of life on Earth
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ABSTRACT: 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 ($E>10^{14}eV;=0.1PeV$) 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'02/2010; -
Article: Possible cosmic ray signatures in clouds?
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ABSTRACT: The role of cosmic rays in cloud formation, by cloud condensation nuclei, is still not fully understood. Although it has been claimed by a number of authors that cosmic ray effects should be small—or even non-existent—it is still argued by others that cosmic ray effects do occur. The present work draws attention to the fact that cosmic rays do not constitute a continuous stream of particles but are characterized by occasional near-simultaneous showers of particles. Under certain circumstances, such showers should leave a signature in clouds—near vertical 'cigar-shaped clouds'—and this work describes their properties. Our own observations have revealed no such structure, but it would be valuable to have a more careful search made.Journal of Physics G Nuclear and Particle Physics 09/2009; 36(11):115202. · 4.18 Impact Factor -
Article: Time variability of high energy cosmic rays
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ABSTRACT: Our model involving cosmic ray acceleration in supernova remnants has been used to predict cosmic ray intensities over long periods of time on a statistical basis. If, as is highly probable, extensive air showers caused by PeV cosmic rays are needed to initiate terrestrial lightning then past dramatic changes in PeV intensities may have had important biological effects. The model has been used to estimate the manner in which the PeV cosmic ray intensity at Earth has varied over the past tens of thousand years. Comment: 11 pages, 5 figures07/2009; -
Article: On the correlation between cosmic ray intensity and cloud cover
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ABSTRACT: 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 replaced06/2009; -
Article: The knee in the cosmic ray energy spectrum
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ABSTRACT: An update of the status of the knee in the cosmic ray energy spectrum at 3-4 PeV is presented. We argue that the evidence in favour of the presence of a 'single source' is even stronger than before. Comment: Proc. 31st Int. Cosm. Ray Conf., Lodz, Poland, 4 pages, 3 figures, ID 030106/2009; -
Article: On the possible connection between cosmic rays and clouds
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ABSTRACT: Various aspects of the connection between cloud cover (CC) and cosmic rays (CR) are analysed. We argue that the anticorrelation between the temporal behaviour of low (LCC) and middle (MCC) clouds evidences against causal connection between them and CR. Nevertheless, if a part of low clouds (LCC) is connected and varies with CR, then its most likely value averaged over the Globe should not exceed 20% at the two standard deviation level. Comment: Proc. 31st Int. Cosm. Ray Conf., Lodz, Poland, 4 pages, 4 figures, ID:0414, acknowledgements replaced06/2009; -
Article: Solar activity and the mean global temperature
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ABSTRACT: The variation with time from 1956-2002 of the globally averaged rate of ionization produced by cosmic rays in the atmosphere is deduced and shown to have a cyclic component of period roughly twice the 11 year solar cycle period. Long term variations in the global average surface temperature as a function of time since 1956 are found to have a similar cyclic component. The cyclic variations are also observed in the solar irradiance and in the mean daily sun spot number. The cyclic variation in the cosmic ray rate is observed to be delayed by 2-4 years relative to the temperature, the solar irradiance and daily sun spot variations suggesting that the origin of the correlation is more likely to be direct solar activity than cosmic rays. Assuming that the correlation is caused by such solar activity, we deduce that the maximum recent increase in the mean surface temperature of the Earth which can be ascribed to this activity is $\lesssim14%$ of the observed global warming. Comment: Accepted for publication in Environmental Research Letters01/2009; -
Article: Gamma Rays frim the Galactic Centre
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ABSTRACT: Recent results from the HESS gamma ray telescope have shown the presence of both a diffuse, extended, flux of gamma rays above ~0.4 TeV and discrete sources in and near the Galactic Centre. Here, we put forward a possible explanation in terms of the diffusion of cosmic ray protons from a succession of supernova remnants (SNR) in the SgrA* region of the Galaxy plus a contribution from SNR in the rest of the Galactic Centre Region, to be called the Galactic Centre Ridge (GCR). Protons are favoured over electrons because the mG magnetic fields in the Region will attenuate energetic electrons severely. Prominent features are the need for 'anomalous diffusion' of the protons in the whole region and the adoption of low efficiency for SNR acceleration in the high density regions. The latter is related by us to the well-known low 'cosmic ray gradient' in the Galaxy. A corroborating feature is the close correlation of inferred cosmic ray intensity with the smoothed intensity of 5 GHZ radio radiation. We attribute this to the presence of the SNR in the GCR. Comment: 21 pages, 7 figures, accepted by J. Phys. G: Nucl. Part. Phys05/2007; -
Article: The Anatomy of the Knee and Gamma-Families
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ABSTRACT: 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.01/2007; -
Article: A fine structure in the gamma-ray sky
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ABSTRACT: 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 4° longitude bin have been determined and compared with the large scale mean found from a 9-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.Journal of Physics G Nuclear and Particle Physics 06/2006; 32(7):1035. · 4.18 Impact Factor -
Article: Cosmic Ray Ions, Dust and the Interstellar Medium
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ABSTRACT: The origin of cosmic rays is a continuing problem in Astrophysics. The majority appear to be of Galactic origin and the manner of acceleration seems to involve ions from the ISM being accelerated by shocks from supernova remnants. Dust in the ISM may also play a part in the early stages. The paper gives a brief account of the origin problem and the likely acceleration mechanisms.Physica Scripta 03/2006; 63(6):504. · 1.20 Impact Factor -
Article: The Anisotropy of Galactic Cosmic Rays as a Product of Stochastic Supernova Explosions
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ABSTRACT: 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 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. Comment: 15 pages, 7 figures, accepted by Astroparticle Physics01/2006; -
Article: The nature of the 'knee' in the cosmic ray energy spectrum
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ABSTRACT: In view of recent developments attention is directed again at two aspects of the well known 'knee' in the cosmic ray energy spectrum at 3 PeV: the mass of the predominant particles at this energy and their source. It is inevitable in a subject such as this that ideas - and conclusions - evolve. Earlier, we had used a particular acceleration model and the nature of the local ISM to infer that the particles are mainly oxygen nuclei. Initially no specific source was identified. More recently, however, we have specified the Monogem Ring supernova remnant (SNR) as the likely source; this is at just the right distance and age and the energies are reasonable. Concerning the mass composition at the knee, a quantity more difficult to determine, recent direct measurements, which extend to higher energies than hitherto, show a likely flattening in the spectrum above 10^4 GeV/nucleon for He-nuclei, a flattening which, if extrapolated to higher energies, would meet the measured spectrum in the knee region. The other nuclei do not show this feature. He-nuclei in the knee region would also be marginally consistent with KASCADE EAS data, although there are serious problems with EAS mass estimates in that experiment. Concerning the acceleration, recent models applied to the Monogem Ring SNR allow a satisfactory explanation in terms of either oxygen or helium, but with the latter being a distinct possibility and perhaps more likely. Comment: 8 pages, 3 figures, accepted by J.Phys.G: Nucl.Part.Phys10/2005;
Top co-authors
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Institutions
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1998–2012
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Durham University
- Department of Physics
Durham, ENG, United Kingdom -
Lebedev Physical Institute of the Russian Academy of Sciences
Moscow, Moscow, Russia
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