Abstract
A numerical simulation of energetic particle motion in the interplanetary medium is carried out using HEOS-2 magnetometer data in order to computeD(μ), the pitch angle diffusion coefficient, where μ is cosine of pitch angle defined with respect to the local field. WhileD(μ) exceeds that given by quasi-linear theory near 90° pitch angle, it is significantly less at higher values of μ, leading to a parallel transport coefficient in good accord with that given by experimental studies of solar proton propagation. In particular, α∥=0.031 AU at a particle magnetic rigidity of 455 MV, while experimental results range from 0.05 to 0.07 AU (+100%, −50%) in this rigidity region. Furthermore, observed approximately μ-dependent solar proton pitch angle distributions are consistent with the computed findingD(μ)/(1 −μ 2)2 ~ constant.
The validity of various analytical corrections to quasi-linear theory as μ→0 are also investigated numerically.
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Moussas, X., Quenby, J.J. The evaluation of the interplanetary diffusion coefficient for energetic particles employing real magnetic field data. Astrophys Space Sci 56, 483–502 (1978). https://doi.org/10.1007/BF01879580
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DOI: https://doi.org/10.1007/BF01879580