Sensitivity of cosmic-ray proton spectra to the low-wavenumber behavior of the 2D turbulence power spectrum
Abstract
In this study, a novel ab initio cosmic ray (CR) modulation code that solves a set of stochastic transport equations
equivalent to the Parker transport equation, and that uses output from a turbulence transport code as input for the
diffusion tensor, is introduced. This code is benchmarked with a previous approach to ab initio modulation. The
sensitivity of computed galactic CR proton spectra at Earth to assumptions made as to the low-wavenumber
behavior of the two-dimensional (2D) turbulence power spectrum is investigated using perpendicular mean free
path expressions derived from two different scattering theories. Constraints on the low-wavenumber behavior of
the 2D power spectrum are inferred from the qualitative comparison of computed CR spectra with spacecraft
observations at Earth. Another key difference from previous studies is that observed and inferred CR intensity
spectra at 73 AU are used as boundary spectra instead of the usual local interstellar spectrum. Furthermore, the
results presented here provide a tentative explanation as to the reason behind the unusually high galactic proton
intensity spectra observed in 2009 during the recent unusual solar minimum
URI
http://hdl.handle.net/10394/18437https://doi.org/10.1088/0004-637X/814/2/152
http://iopscience.iop.org/article/10.1088/0004-637X/814/2/152