The Evaluation of the Interplanetary Diffusion Coefficient for Energetic Particles Employing Real Magnetic Field Data
Abstract
A numerical simulation of energetic particle motion in the interplanetary medium is carried out using HEOS2 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 quasilinear 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 μdependent solar proton pitch angle distributions are consistent with the computed findingD(μ)/(1 μ ^{2})^{2} ~ constant. The validity of various analytical corrections to quasilinear theory as μ→0 are also investigated numerically.
 Publication:

Astrophysics and Space Science
 Pub Date:
 July 1978
 DOI:
 10.1007/BF01879580
 Bibcode:
 1978Ap&SS..56..483M
 Keywords:

 Diffusion Coefficient;
 Energetic Particles;
 Interplanetary Magnetic Fields;
 Interplanetary Medium;
 Solar Protons;
 Solar Wind;
 Graphs (Charts);
 Heos Satellites;
 Magnetic Field Configurations;
 Mathematical Models;
 Perturbation Theory;
 Pitch (Inclination);
 Propagation Modes;
 Space Radiation