DISCREPANT HARDENING OBSERVED IN COSMIC-RAY ELEMENTAL SPECTRA

Journal Article · Sat May 01 00:00:00 EDT 2010 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/714/1/L89; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)· OSTI ID:21305005

Ahn, H S; Ganel, O; Han, J H; Kim, K C; Lee, M H; Lutz, L; Malinin, A ^[1]; Allison, P; Beatty, J J ^[2]; Bagliesi, M G; Bigongiari, G; Maestro, P; Marrocchesi, P S ^[3]; Childers, J T; DuVernois, M A ^[4]; Conklin, N B; Coutu, S; Mognet, S I ^[5]; Jeon, J A ^[6]

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1. Institute for Physical Science and Technology, University of Maryland, College Park, MD 20742 (United States)
2. Department of Physics, Ohio State University, Columbus, OH 43210 (United States)
3. Department of Physics, University of Siena and INFN, Siena 53100 (Italy)
4. School of Physics and Astronomy, University of Minnesota, MN 55414 (United States)
5. Department of Physics, Penn State University, University Park, PA 16802 (United States)
6. Department of Physics, Ewha Womans University, Seoul 120-750 (Korea, Republic of)

The balloon-borne Cosmic Ray Energetics And Mass experiment launched five times from Antarctica has achieved a cumulative flight duration of about 156 days above 99.5% of the atmosphere. The instrument is configured with complementary and redundant particle detectors designed to extend direct measurements of cosmic-ray composition to the highest energies practical with balloon flights. All elements from protons to iron nuclei are separated with excellent charge resolution. Here, we report results from the first two flights of {approx}70 days, which indicate hardening of the elemental spectra above {approx}200 GeV/nucleon and a spectral difference between the two most abundant species, protons and helium nuclei. These results challenge the view that cosmic-ray spectra are simple power laws below the so-called knee at {approx}10{sup 15} eV. This discrepant hardening may result from a relatively nearby source, or it could represent spectral concavity caused by interactions of cosmic rays with the accelerating shock. Other possible explanations should also be investigated.

• OSTI ID: 21305005
• Journal Information: Astrophysical Journal Letters, Vol. 714, Issue 1; Other Information: DOI: 10.1088/2041-8205/714/1/L89; Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE
ACCELERATION
ATMOSPHERES
BALLOONS
COSMIC RADIATION
HELIUM
IRON
PROTONS
SPECTRA
SUPERNOVAE