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A positivity-preserving multiscale method for plasma simulation
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DOI：10.1016/j.cnsns.2026.109826.png)
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Abstract
En 中文
• A temporally second-order positivity-preserving unified gas-kinetic scheme (UGKS) is developed for plasma simulations within a finite-volume discrete-velocity framework. • A rigorous equivalence between the finite-volume UGKS update and the time-evolution integral representation of the transport–collision equation is established and extended from first-order to second-order temporal accuracy. • The second-order positivity-preserving formulation is essential for Strang splitting, ensuring that the overall coupled Vlasov–BGK solver maintains global second-order temporal accuracy. • The proposed scheme preserves positivity, asymptotic-preserving (AP) property, and multiscale consistency uniformly with respect to the relaxation parameter. • Strict positivity proofs are provided based on the convex-combination structure of the time-evolution solution, avoiding restrictive time-step constraints. • Numerical experiments, including weak and strong Landau damping and two-stream instability, validate the accuracy, robustness, and theoretical properties of the method.
Keywords:
Positivity-preserving
Unified gas-kinetic scheme
Plasma simulation
Multiscale consistency
Asymptotic-preserving
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