The Effects of the Dissipation Range on the Spatial Diffusion of Energetic Charged Particles

C. W. Smith, J. W. Bieber and W. H. Matthaeus

Proceedings of the 21st International Cosmic Ray Conference (Adelaide), 5, 284-287 (1990)

Abstract:

New conclusions as to the form of the Fokker-Planck coefficient for the pitch angle scattering of cosmic rays in magnetic field turbulence can be obtained if a dissipation range is incorporated into the turbulence model. Examination of the pitch angle diffusion coefficient for particles with pitch angles near 90 degrees shows that the coefficient goes to zero more quickly as the pitch angle nears 90 degrees than was previously indicated, resulting in a spatial diffusion coefficient that is infinite for both isotropic and slab geometries and exceeds the singular behavior previously noted by Fisk et al. (1974). This result follows directly from the presence of dissipation, is applicable to particles of any energy, and points once again to the need to develop a correct higher order theory of pitch angle scattering for particles near 90 degrees.