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Title: DISCREPANT HARDENING OBSERVED IN COSMIC-RAY ELEMENTAL SPECTRA

Abstract

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.

Authors:
; ; ; ; ; ;  [1]; ;  [2]; ; ; ;  [3]; ;  [4]; ; ;  [5];  [6]
  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)
Publication Date:
OSTI Identifier:
21305005
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal Letters
Additional Journal Information:
Journal Volume: 714; Journal Issue: 1; Other Information: DOI: 10.1088/2041-8205/714/1/L89; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 2041-8205
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; 99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE; ACCELERATION; ATMOSPHERES; BALLOONS; COSMIC RADIATION; HELIUM; IRON; PROTONS; SPECTRA; SUPERNOVAE

Citation Formats

Ahn, H S, Ganel, O, Han, J H, Kim, K C, Lee, M H, Lutz, L, Malinin, A, Allison, P, Beatty, J J, Bagliesi, M G, Bigongiari, G, Maestro, P, Marrocchesi, P S, Childers, J T, DuVernois, M A, Conklin, N B, Coutu, S, Mognet, S I, Jeon, J A, and Minnick, S. DISCREPANT HARDENING OBSERVED IN COSMIC-RAY ELEMENTAL SPECTRA. United States: N. p., 2010. Web. doi:10.1088/2041-8205/714/1/L89; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA).
Ahn, H S, Ganel, O, Han, J H, Kim, K C, Lee, M H, Lutz, L, Malinin, A, Allison, P, Beatty, J J, Bagliesi, M G, Bigongiari, G, Maestro, P, Marrocchesi, P S, Childers, J T, DuVernois, M A, Conklin, N B, Coutu, S, Mognet, S I, Jeon, J A, & Minnick, S. DISCREPANT HARDENING OBSERVED IN COSMIC-RAY ELEMENTAL SPECTRA. United States. https://doi.org/10.1088/2041-8205/714/1/L89; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)
Ahn, H S, Ganel, O, Han, J H, Kim, K C, Lee, M H, Lutz, L, Malinin, A, Allison, P, Beatty, J J, Bagliesi, M G, Bigongiari, G, Maestro, P, Marrocchesi, P S, Childers, J T, DuVernois, M A, Conklin, N B, Coutu, S, Mognet, S I, Jeon, J A, and Minnick, S. 2010. "DISCREPANT HARDENING OBSERVED IN COSMIC-RAY ELEMENTAL SPECTRA". United States. https://doi.org/10.1088/2041-8205/714/1/L89; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA).
@article{osti_21305005,
title = {DISCREPANT HARDENING OBSERVED IN COSMIC-RAY ELEMENTAL SPECTRA},
author = {Ahn, H S and Ganel, O and Han, J H and Kim, K C and Lee, M H and Lutz, L and Malinin, A and Allison, P and Beatty, J J and Bagliesi, M G and Bigongiari, G and Maestro, P and Marrocchesi, P S and Childers, J T and DuVernois, M A and Conklin, N B and Coutu, S and Mognet, S I and Jeon, J A and Minnick, S.},
abstractNote = {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.},
doi = {10.1088/2041-8205/714/1/L89; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)},
url = {https://www.osti.gov/biblio/21305005}, journal = {Astrophysical Journal Letters},
issn = {2041-8205},
number = 1,
volume = 714,
place = {United States},
year = {Sat May 01 00:00:00 EDT 2010},
month = {Sat May 01 00:00:00 EDT 2010}
}