Technical Objective of Space Radiations Section

The overall technical objective of this work unit (Proposal # 76-P071-10), starting FY 2010, is to solve the problem of the origin of the cosmic rays, which are energetic charged particles composed mainly of protons and ions that were discovered in 1912. Cosmic rays are an important particle background in the space radiation environment. The recent deployment of radiation detectors and telescopes on ground and in space, in particular, the Fermi Gamma Ray Space Telescope, presents a unique opportunity to achieve this goal by providing new data sets for analysis and interpretation.

Because of magnetic fields in interstellar space, cosmic rays do not point directly to their sources. Gamma rays indicate sites of high-energy particles, but can be attenuated by matter or other photons at the source or in transit from the source to Earth. Neutrinos would unambiguously point to the sources of the cosmic rays, but are faint and difficult to detect. The solution to the cosmic-origin problem can best be achieved by jointly analyzing high-energy space radiations, including gamma rays, cosmic rays, and neutrinos.

This research is also used to secure a basic understanding of nonthermal radiation processes, to interpret data from spacecraft designed and built through DoD and NASA funds, and to identify science goals for planned high-energy radiation detectors in space. This research addresses the Navy S&T operational environments objective of understanding space environmental effects---the near-earth space radiation environment and space weather---and their impact on operations. Another important goal of this research is to provide scientific motivation for an Advanced Compton Telescope mission to measure nuclear gamma-ray line emission from Solar flares, explosive astrophysical sources, compact objects, and cosmic ray interactions with the interstellar medium.