67 research outputs found
Spectra of magnetic fluctuations and relativistic particles produced by a nonresonant wave instability in supernova remnant shocks
We model strong forward shocks in young supernova remnants with efficient
particle acceleration where a nonresonant instability driven by the cosmic ray
current amplifies magnetic turbulence in the shock precursor. Particle
injection, magnetic field amplification (MFA) and the nonlinear feedback of
particles and fields on the bulk flow are derived consistently. The shock
structure depends critically on the efficiency of turbulence cascading. If
cascading is suppressed, MFA is strong, the shock precursor is stratified, and
the turbulence spectrum contains several discrete peaks. These peaks, as well
as the amount of MFA, should influence synchrotron X-rays, allowing
observational tests of cascading and other assumptions intrinsic to the
nonlinear model of nonresonant wave growth.Comment: 3 figures, 5 pages. Accepted for publication in ApJ
Testing the Origin of High-Energy Cosmic Rays
Recent accurate measurements of cosmic-ray (CR) protons and nuclei by ATIC-2,
CREAM, and PAMELA reveal: a) unexpected spectral hardening in the spectra of CR
species above a few hundred GeV per nucleon, b) a harder spectrum of He
compared to protons, and c) softening of the CR spectra just below the break
energy. These newly-discovered features may offer a clue to the origin of the
observed high-energy Galactic CRs. We discuss possible interpretations of these
spectral features and make predictions for the secondary CR fluxes and
secondary to primary ratios, anisotropy of CRs, and diffuse Galactic
{\gamma}-ray emission in different phenomenological scenarios. Our predictions
can be tested by currently running or near-future high-energy astrophysics
experiments.Comment: 23 pages, 14 color figures. Accepted for publication in Ap
Collinear matching for Sivers function at next-to-leading order.
We evaluate the light-cone operator product expansion for unpolarized transverse momentum dependent (TMD) operator in the background-field technique up twist-3 inclusively. The next-to-leading order (NLO) matching coefficient for the Sivers function is derived. The method, as well as many details of the calculation are presented
- …