Heliospheric solar wind turbulence model with implications for ab initio modulation of cosmic rays

Abstract

Cosmic rays as they pass through the heliosphere carry information about the properties and structure of the heliosphere and undergo modulation due to interaction with small‐scale and large‐scale solar wind structures, including turbulence. Here, governing equations for correlation length, variance, and temperature are described to account for turbulence in the heliosphere. This extends a one‐dimensional (radial) turbulence code in a simple way to produce a two‐dimensional (radial, latitudinal) code valid in the heliosphere spanning from close to the Sun up to 100 AU. The resulting two‐dimensional version of the turbulence code is then integrated into an ab initio modulation code. The diffusion coefficients are calculated using our present understanding of the turbulence, not using ad hoc assumptions as have been reported in the past. By advancing such a theory for solar wind turbulence, we describe its implications for cosmic rays. The resulting radial profile in the equatorial plane and spectrum in the equatorial plane at various radial distances compare well with observations.