Report

Global Anisotropies in TeV Cosmic Rays Related to the Sun’s Local Galactic Environment from IBEX

Science  28 Feb 2014:
Vol. 343, Issue 6174, pp. 988-990
DOI: 10.1126/science.1245026

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Ordering Cosmic Rays

Earth and other planets are constantly bombarded by cosmic rays (charged particles from the cosmos). The flux of very-high-energy cosmic rays varies according to where we look in the sky. Schwadron et al. (p. 988, published online 13 February) show that recent measurements of the local interstellar parameters by NASA's Interstellar Boundary Explorer satellite are consistent with observed cosmic ray anisotropies at tera–electron volt energies, implying that local interstellar conditions play a role in ordering very-high-energy cosmic rays in our cosmic vicinity.

Abstract

Observations with the Interstellar Boundary Explorer (IBEX) have shown enhanced energetic neutral atom (ENA) emission from a narrow, circular ribbon likely centered on the direction of the local interstellar medium (LISM) magnetic field. Here, we show that recent determinations of the local interstellar velocity, based on interstellar atom measurements with IBEX, are consistent with the interstellar modulation of high-energy (tera–electron volts, TeV) cosmic rays and diffusive propagation from supernova sources revealed in global anisotropy maps of ground-based high-energy cosmic-ray observatories (Milagro, Asγ, and IceCube). Establishing a consistent local interstellar magnetic field direction using IBEX ENAs at hundreds to thousands of eV and galactic cosmic rays at tens of TeV has wide-ranging implications for the structure of our heliosphere and its interactions with the LISM, which is particularly important at the time when the Voyager spacecraft are leaving our heliosphere.

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