On the pitch-angle-dependent perpendicular diffusion coefficients of solar energetic protons in the inner heliosphere

Abstract

Various numerical solar energetic particle (SEP) transport studies have shown that perpendicular diffusion plays a significant role in the propagation of these particles in the heliosphere. In particular, computed SEP intensities and anisotropies have been shown to be sensitive to the pitch-angle dependence of the perpendicular diffusion coefficient as well as its magnitude. This study proposes a novel approach to the calculation of this quantity and compares this to the results of previous theoretical approaches. These various perpendicular diffusion coefficient expressions are demonstrated for turbulence conditions prevalent at Earth and closer to the Sun