Speaker
David Ruffolo
(Mahidol University)
Description
Nonlinear guiding center (NLGC) theory has been used to explain the asymptotic perpendicular diffusion coefficient
κ⊥ of energetic charged particles in a turbulent magnetic field, which can be applied to better understand cosmic
ray transport. Here we re-derive NLGC, replacing the assumption of diffusive decorrelation with random ballistic
decorrelation (RBD), which yields an explicit formula for κ⊥.We note that scattering processes can cause a reversal
of the guiding center motion along the field line, i.e., “backtracking,” leading to partial cancellation of contributions
to κ⊥, especially for low-wavenumber components of the magnetic turbulence. We therefore include a heuristic
backtracking correction (BC) that can be used in combination with RBD. In comparison with computer simulation
results for various cases and two different magnetic field models (2D+slab and noisy RMHD), NLGC with RBD and BC provides a substantially improved characterization of the
perpendicular diffusion coefficient for a fluctuation amplitude less than or equal to the large-scale magnetic field. Partially supported by the Thailand Research Fund, the Development
and Promotion of Science and Technology Talents Project of
the Royal Thai Government, the U.S. NSF (AGS-1063439
and SHINE AGS-1156094), NASA (Heliophysics Theory
NNX11AJ4G), the Solar Probe Plus/ISIS project, and
Thailand’s
Ministry of Education.
| Registration number following "ICRC2015-I/" | 262 |
|---|---|
| Collaboration | -- not specified -- |
Author
David Ruffolo
(Mahidol University)
Co-authors
Dr
Andrew Snodin
(King Mongkut's University of Technology North Bangkok)
Dr
Piyanate Chuychai
(Mae Fah Luang University)
Mr
Taweesak Jitsuk
(Mahidol University)
Mr
Theerasarn Pianpanit
(Mahidol University)
Prof.
William H. Matthaeus
(University of Delaware)
