Semi-Implicit Continuum Kinetic Modeling of Weakly Collisional Parallel Transport in a Magnetic Mirror
Abstract
We present implicit-explicit (IMEX) kinetic simulations of weakly collisional parallel plasma transport in magnetic mirror configurations using the continuum code \textsc{COGENT}. The numerical scheme employs a Jacobian-free Newton--Krylov method with algebraic multigrid preconditioning to overcome the severe time-step limitations imposed by strong mirror forces in fully explicit schemes. Applied to parameters relevant to the WHAM mirror experiment, the IMEX approach enables time steps up to times larger than those permitted by explicit methods, resulting in a 2500x speedup in 1D--2V simulations of parallel transport with kinetic ions and Boltzmann electrons. Additionally, a reduced bounce-averaged model for a square mirror is implemented to support the computationally intensive fully kinetic simulations. The bounce-averaged formulation is used to evaluate the numerical convergence of the velocity-space discretization algorithms and to assess the role of the collision model by comparing simulations employing the nonlinear Fokker--Planck and the simplified Lenard--Bernstein--Dougherty collision operators.
Cite
@article{arxiv.2507.19729,
title = {Semi-Implicit Continuum Kinetic Modeling of Weakly Collisional Parallel Transport in a Magnetic Mirror},
author = {M. Dorf and M. Dorr and V. Geyko and D. Ghosh and M. Umansky and J. Angus},
journal= {arXiv preprint arXiv:2507.19729},
year = {2025}
}