The Highest energy cosmic rays

1990
22 pages
Published in:
  • Nucl.Phys.B Proc.Suppl. 22 (1991) 116-137

Citations per year

1991199920072015202302468
Abstract: (Elsevier)
The experimental work on the energy spectrum, mass composition and arrival direction distribution of cosmic rays above 10 18 eV is reviewed. Particular attention is given to the various measurements which have been made of the cosmic ray energy spectrum, including a detailed discussion of cross-calibration procedures. It is concluded that the evidence favours a spectral slope which is steeper ( γ >3) above 10 18 eV than below, but beyond 10 19 eV the slope flattens again with γ = 2.5 ± 0.2. Shower events produced by cosmic rays well in excess of 5 × 10 19 eV certainly exist and there is no evidence of a cut-off in the energy spectrum at least to 10 20 eV. The rudimentary evidence on mass composition, interpreted with a simple two mass component model, suggssts that the composition is mixed at least to 10 18 eV with evidence against significant further iron enrichment beyond. Measurements of arrival directions are also limited although recent analysis lends support to a picture in which there is increasing anisotropy associated with the galactic plane up to 10 19 eV. Above this energy the limited data support the view that there is an extra-galactic anisotropy, perhaps associated with the Virgo Supercluster. These overall conclusions are not particularly new; rather the recent evidence and new analyses have served to strengthen similar views reached some years ago: it is very clear that exposures of at least 1000km 2 per year are needed if the field is to advance substantially over the next decade.
  • review
  • cosmic radiation: energy spectrum
  • energy spectrum: cosmic radiation
  • cosmic radiation: mass spectrum
  • mass spectrum: cosmic radiation
  • cosmic radiation: anisotropy
  • showers
  • experimental results
  • bibliography
  • > 10**9 GeV