COSMIC-RAY SMALL-SCALE ANISOTROPIES AND LOCAL TURBULENT MAGNETIC FIELDS

• Published in: The Astrophysical Journal
• Main Authors: Lopez-Barquero, V., Farber, R., Xu, S., Desiati, P., Lazarian, A.
• Other Authors: Lopez-Barquero, V (reprint author), Univ Wisconsin, Dept Phys, Madison, WI 53706 USA., Univ Wisconsin, Dept Phys, Madison, WI 53706 USA., Wheaton Coll, Dept Phys & Astron, Norton, MA 02766 USA., Peking Univ, Sch Phys, Dept Astron, Beijing 100871, Peoples R China., Univ Wisconsin, WIPAC, Madison, WI 53703 USA., Univ Wisconsin, Dept Astron, Madison, WI 53706 USA.
• Format: Journal/Newspaper
• Language: English
• Published: ASTROPHYSICAL JOURNAL 2016
• Subjects: cosmic rays; magnetic fields; magnetohydrodynamics (MHD); scattering; turbulence; COMPRESSIBLE MAGNETOHYDRODYNAMIC TURBULENCE; ENERGETIC PARTICLE ANISOTROPIES; AIR-SHOWER ARRAY; ARRIVAL DIRECTIONS; INTERSTELLAR TURBULENCE; TEV; TRANSPORT; RECONNECTION; PROPAGATION; ICECUBE; Reu; National Science Foundation Office of Polar Programs
• Online Access: https://hdl.handle.net/20.500.11897/458732; https://doi.org/10.3847/0004-637X/830/1/19

Cosmic-ray anisotropy has been observed in a wide energy range and at different angular scales by a variety of experiments over the past decade. However, no comprehensive or satisfactory explanation has been put forth to date. The arrival distribution of cosmic. rays at Earth is the convolution of the distribution of their sources and of the effects of geometry and properties of the magnetic field through which particles propagate. It is generally believed that the anisotropy topology at the largest angular scale is adiabatically shaped by diffusion in the structured interstellar magnetic field. On the contrary, the medium-and small-scale angular structure could be an effect of nondiffusive propagation of cosmic. rays in perturbed magnetic fields. In particular, a possible explanation for. the observed small-scale anisotropy observed at the. TeV energy scale. may be the effect of particle propagation in turbulent magnetized plasmas. We perform numerical integration of test particle trajectories in low-beta compressible magnetohydrodynamic turbulence to study how the cosmic. rays' arrival direction distribution is perturbed when they stream along the local turbulent magnetic field. We utilize Liouville's theorem for obtaining the anisotropy at Earth and provide the theoretical framework for the application of the theorem in the specific case of cosmic-ray arrival distribution. In this work, we discuss the effects on the anisotropy arising from propagation in this inhomogeneous and turbulent interstellar magnetic field. NSF [AST 0808118]; NASA [NNX14AJ53G]; WIPAC; U.S. National Science Foundation-Office of Polar Programs; Brazil-US Physics Ph.D. Student and Post-doc Visitation Program; Research Experiences for Undergraduates (REU) Program of the National Science Foundation [AST-1004881] SCI(E) ARTICLE 1 830