by Peter K F Grieder, Springer. Hardback ISBN 9783540769415, £314 (€368.20, $469).
Peter Grieder has compiled an exceptional collection of information and data on a major area of cosmic-ray physics: the air showers that are the observable results of energetic cosmic rays incident on the Earth’s atmosphere. The subtitle correctly identifies this two-volume (1000 pages) book as a very complete and valuable resource for physicists working in this domain of cosmic-ray physics. It is also a most relevant and appropriate follow-on to Grieder’s 2001 book, Cosmic Rays at Earth.
The flux of cosmic rays falls approximately as the cube of the energy (at energies above a few giga-electron-volts), so the flux above about 1014 eV is too low to study by direct (balloon or satellite) observation. Hence our knowledge of this astroparticle physics domain at higher energies is totally dependent on observations from the Earth, which in turn relate to the interactions of the primary cosmic rays in the Earth’s atmosphere and the subsequent cascades – the air showers. For example, at energies above about 1019 eV, the flux of primary cosmic rays is only about one per square kilometre per year per steradian. The nuclear composition, energy spectrum, and astronomical sources of these unusually energetic particles are of great interest, but the means of studying them are totally dependent on understanding their interactions in the atmosphere and the resulting air showers.
These two volumes provide an excellent resource for understanding all of the relevant consequences and observables of these air showers: the hadron, muon, electron-photon, and even neutrino fluxes, their spatial and angular distributions, and their energy spectra. Grieder also discusses the various detection technologies: surface arrays of scintillation or water Cherenkov counters, muon counters, atmospheric fluorescence and air Cherenkov radiation detectors. Even novel technologies, such as the radio detection and study of air showers, are presented and discussed. The first volume, Part I, deals mainly with the basic theoretical framework of the processes that determine an air shower, while the second volume, Part II, consists primarily of a compilation of experimental data and related discussions, as well as predictions and discussions of individual air-shower constituents.
The collection of data and graphs from a great multitude of experimental observations is overwhelming, and most interesting. The strong-interaction physics that governs the behaviour of the interactions and the consequent reaction product numbers, energies, and angular distributions are also discussed, together with various Monte Carlo models that form the basis for the calculations of the observables. As the primary interactions of the higher-energy cosmic rays are at energies above those for which detailed inclusive distributions have been studied with particle accelerators, there remain uncertainties in the Monte Carlos and the consequent interpretation of these air-shower observables. Hence, while the energies of the primary cosmic rays can be reasonably well determined (from the total energy of the electromagnetic cascade plus observed muons and hadrons), some uncertainty in the atomic masses of the observed highest energy incident cosmic rays remains.
Although the most energetic cosmic rays are nuclei, astronomical gamma rays also initiate air showers, and it is relevant to discriminate between these and hadron-initiated showers. As with nuclear cosmic rays, direct satellite observation of the gamma radiation is being actively pursued. However at higher energies (above about 1 TeV), surface installations that observe the gamma-initiated air showers, often with air Cherenkov detectors, are important. The characteristics of gamma-ray initiated showers and the relevant detector technologies are also discussed.
An extensive appendix in Part II identifies 65 air-shower observation installations, past and present, around the world, and notes their relevant properties such as altitude (many at elevations above 3000 m) and atmospheric depth, the energy thresholds of their muon detectors, and other characteristics. Sketches of the detector configurations of about half of them are also included. In addition, more than 30 underground (and underwater/under-ice) muon and neutrino detectors – past and present – are described.
This two-volume book certainly merits acquisition by groups working actively on air showers, the installations, data analysis, and physics interpretation. I am sure that it will prove to be an invaluable resource in this lively area of astroparticle physics.
