No 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 contibution 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.

The advent of new and improved extensive air shower (EAS) arrays - and the attendant generation of data of higher statistical precision than hitherto - has led us to return to an old problem: the origin of the change in spectral slope at an energy of eV. The data recorded are the so-called shower size spectra at ground level, i.e. the spectrum of the total number of cosmic rays inferred for each shower, and we use results from seven arrays which are situated at levels ranging from near sea level to half way up the atmosphere (in terms of atmospheric mass per unit area). The method adopted by us is a new one which enables the combination of experimental data in such a way that previously unrecognized features are now apparent. We present evidence for a spectral shape of the shower size spectrum, and thus the primary particle energy spectrum, which has the signature of an extra component from a single source which protrudes above the `background' due to many other cosmic ray sources in the Galaxy. It is proposed that the `single source' is a local supernova remnant.

A decrease in the globally averaged low level cloud cover, deduced from the ISCCP infrared data, as the cosmic ray intensity decreased during the solar cycle 22 was observed by two groups. The groups went on to hypothesize that the decrease in ionization due to cosmic rays causes the decrease in cloud cover, thereby explaining a large part of the currently 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.

We have cross‐correlated the WMAP data with several surveys of extragalactic sources and find evidence for temperature decrements associated with galaxy clusters and groups detected in the APM Galaxy Survey and the Abell–Corwin–Olowin (ACO) catalogue. We interpret this as evidence for the thermal Sunyaev–Zel'dovich (SZ) effect from the clusters. Most interestingly, the signal may extend to ≈ 1 deg (≈5 h−1 Mpc) around both groups and clusters and we suggest that this may be due to hot ‘supercluster’ gas. We have further cross‐correlated the WMAP data with clusters identified in the 2MASS galaxy catalogue and also find evidence for temperature decrements there. From the APM group data we estimate the mean Compton parameter as y(z < 0.2) = 7 ± 3.8 × 10−7. We have further estimated the gas mass associated with the galaxy group and cluster haloes. Assuming temperatures of 5 keV for ACO clusters and 1 keV for APM groups and clusters, we derive average gas masses of M(r < 1.75 h−1 Mpc) ≈ 3 × 1013h−2 M⊙ for both, the assumed gas temperature and SZ central decrement differences approximately cancelling. Using the space density of APM groups we then estimate Ωgas0≈ 0.03 h−1 (1 keV/kT)(θmax/20 arcmin)0.75. For an SZ extent of θmax= 20 arcmin, kT= 1 keV and h= 0.7, this value of Ωgas0≈ 0.04 is consistent with the standard value of Ωbaryon0= 0.044, but if the indications we have found for a more extended SZ effect out to θmax≈ 60 arcmin are confirmed, then higher values of Ωgas0 will be implied. Finally, the contribution to the WMAP temperature power spectrum from the extended SZ effect around the z < 0.2 APM+ACO groups and clusters is 1–2 orders of magnitude lower than the l= 220 first acoustic peak. But if a similar SZ effect arises from more distant clusters then this contribution could increase by a factor >10 and then could seriously affect the WMAP cosmological fits.