Modeling Galactic Cosmic Rays in the Very Local Interstellar Medium
Abstract
The very local interstellar medium (VLISM) presents significant challenges for energetic particle modeling because of the presence of both incompressible and compressive turbulent magnetic fluctuations (in the sense of the presence of the magnetic fluctuation component parallel to the mean field) that makes it a very distinct transport environment compared with the more familiar solar wind. This paper presents a pitch-angle dependent diffusive transport model in two-dimensional, compressive turbulence, and a framework for computer modeling of charged particles with high velocities applicable to galactic cosmic rays (GCRs). The model elaborates on existing weakly nonlinear theories of perpendicular diffusion in the limit of weak pitch-angle scattering combined with possibly rapid diffusive motion of the guiding center normal to the magnetic field. The numerical framework is based in the SPECTRUM (Space Plasma and Energetic Charged particle TRansport on Unstructured Meshes) suite of simulation codes. Two representative simulations are presented. The first is a high-resolution study of GCR transport in the VLISM region with a particular emphasis on the distribution of the heliopause crossing points. This model uses an analytic formalism for the magnetic field draping around the hsurface of the heliopause. The second case is a simulation of GCRs in a mesh-based representation of the heliosphere derived from MHD simulations converged to a steady state, developed for the SHIELD project. The results are discussed in the context of the earlier model based on the nearly isotropic (Parker) formalism.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFMSH31B..04F