Published March 1999 | Version v1
Journal article

Are we making progress in finding the sources of the most energetic cosmic rays?

Creators

Description

There is progress, in the sense that although the energies assigned to cosmic rays by air shower arrays may need reducing by about 20%, energy measurements are consistent at about this level, and several experiments now accord with a spectrum which astonishingly shows no GZK cut-off near 1020 eV, greatly limiting the possible source regions. The simplest interpretation is that few cosmic rays above 1019 eV come from hundreds of Mpc, contrary to expectation on geometrical grounds. Most of the arrival directions of showers above 4 x 1019 eV show little correlation with the supergalaxy or with matter concentrations within 200 Mpc. The implications of the spectrum and the arrival directions are discussed. The most likely explanations of their unexpected features are either (a) that these cosmic rays come mainly from the decay of cosmological relic particles clustered in a large galactic halo (though not if photons really do form a large part of the decay spectrum), or (b) that local intergalactic magnetic fields are unexpectedly strong, and disguise the position of and enhance one extraordinary source within a few Mpc, or (c) most particles above 1019 eV are very different from protons after all, and do not have a threshold for serious energy loss as low as 1020 eV, or (d) that there is a conspiracy of matching fluxes, so that most cosmic rays above 1019 eV are from widespread extragalactic sources, but a superimposed hard spectrum from decaying halo relic particles neatly reduces the magnitude of the GZK fall-off above 1020 eV. Several close pairs of arrival directions may yet turn out to be accidental, but if not, explanations (a) and (b) fail. There are several diagnostic tests to be made by the well-placed first (Southern) Auger Project detector and the High-Resolution Fly's Eye detector

Additional details

Identifiers

PII
S0920563299002212;

Publishing Information

Journal Title
Nuclear Physics. B, Proceedings Supplements
Journal Volume
75
Journal Issue
1-2
Journal Page Range
p. 109-118
ISSN
0920-5632
CODEN
NPBSE7

Conference

Title
10. international symposium on very high energy cosmic ray interactions
Dates
12-17 Jul 1998
Place
Assergi (Italy)

INIS

Country of Publication
Netherlands
Country of Input or Organization
International Atomic Energy Agency (IAEA)
INIS RN
34060149
Subject category
S72: PHYSICS OF ELEMENTARY PARTICLES AND FIELDS;
Resource subtype / Literary indicator
Conference
Descriptors DEI
ANGULAR DISTRIBUTION; COSMIC RAY SOURCES; COSMOLOGY; ENERGY SPECTRA; EXTENSIVE AIR SHOWERS; INTERGALACTIC SPACE; RADIATION DETECTORS
Descriptors DEC
COSMIC RADIATION; COSMIC SHOWERS; DISTRIBUTION; IONIZING RADIATIONS; MEASURING INSTRUMENTS; RADIATIONS; SECONDARY COSMIC RADIATION; SHOWERS; SPACE; SPECTRA

Optional Information

Copyright
Copyright (c) 1999 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.