Cosmic Ray Program Assessment Group

• Main Authors: Point-of-contact Donald, C. Ellison, W. Robert Binns, John Krizmanic, Goddard Space, Igor V. Moskalenko, Jonathan Ormes, Andrew Westphal
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Antarctic; Milky Way; The Antarctic; Antarc*
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.610.1163; http://cosmicray.umd.edu/vision2020/images/stories/file/RFI_25mar09_F.pdf

Key Science Goals (5 pages) Cosmic-ray astrophysics is on the verge of a decade of great discovery. There is now convincing evidence from TeV gamma-ray and X-ray synchrotron observations that cosmic-ray electrons are produced in young supernova remnants (SNRs) and the proof for cosmic-ray ion production in SNRs may soon come with Fermi (formerly GLAST) observations. The sources of the highest energy cosmic rays are less certain, other than that they must originate from beyond the Milky Way Galaxy, but great progress in determining their origin has been made by the Auger and HiRes telescopes. These telescopes have shown that cosmic rays with energies above ~1019 eV obey the so-called Greisen-Zatsepin-Kuzmin (GZK) cutoff and may well be correlated with active galactic nuclei (AGN). At lower energies, progress has been made in measuring spectra of individual elements (e.g., Fig. 1), and long-duration balloon flights flying multiple circumnavigations of the Antarctic continent (see Fig. 5), promise to extend these measurements to ~1015 eV, close to the cosmic-ray “knee. ” If sufficient resources are available in the next decade, cosmic rays can address questions as important as any in astrophysics such as determining how the elements are created and distributed, identifying the nearest sources of