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 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.
- 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