Abstract Details
Abstracts
Author: Federico D Halpern
Requested Type: Poster
Submitted: 2024-04-01 16:08:27
Co-authors: O.Issan, O.Koshkarov, G.L.Delzanno
Contact Info:
General Atomics
3550 General Atomics Ct
San Diego, CA 92121
United States
Abstract Text:
In a recent paper, we analyzed the physics and numerical properties of the 1D1V Vlasov-Poisson (VP) system using a new approach based on orthogonal Hermite decomposition of the square root of the distribution function [1]. This work expands and extend our previous efforts in order to better understand the relationship of the anti-symmetric Vlasov-Poisson model to measurable fluid quantities (density, momentum, energy, and beyond). Unlike conventional orthogonal decompositions based on f, the new square-root-f anti-symmetric model does not possess a simple correspondence between individual Hermite bases and a corresponding fluid moments. Instead, we find that, while all fluid moments can be reconstructed from VP, even the plasma density results from a coupling of all the Hermite bases. The moment reconstruction can be formally carried out using an infinite series of associated velocity moments, which obey an integral from of the anti-symmetric VP force operator. Interestingly, the anti-symmetry of the force operator allows us to derive closed expressions for all the velocity moments, showing that they can all be conserved. In order to fulfill the conservation relation, it becomes essential to use a suitable Poisson equation for the electric field. In numerical applications, there can be numerical drift due to truncation of the series. As examples of the conservation properties of the formulation we show numerical verification of benchmark problems including linear and nonlinear Landau damping, two-stream instability, and bump-on-tail instability.
[1] O.Issan et al., Anti-symmetric and positivity-preserving formulation of a spectral method for Vlasov-Poisson equations, Journal of Computational Physics (2024, under review)
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