Steepest-descent algorithm for simulating plasma-wave caustics via metaplectic geometrical optics

Abstract

The design and optimization of radiofrequency-wave systems for fusion applications is often performed using ray-tracing codes, which rely on the geometrical-optics (GO) approximation. However, GO fails at wave cutoffs and caustics. To accurately model the wave behavior in these regions, more advanced and computationally expensive "full-wave" simulations are typically used, but this is not strictly necessary. A new generalized formulation called metaplectic geometrical optics (MGO) has been proposed that reinstates GO near caustics. The MGO framework yields an integral representation of the wavefield that must be evaluated numerically in general. We present an algorithm for computing these integrals using Gauss-Freud quadrature along the steepest-descent contours. Benchmarking is performed on the standard Airy problem, for which the exact solution is known analytically. The numerical MGO solution provided by the new algorithm agrees remarkably well with the exact solution and significantly improves upon previously derived analytical approximations of the MGO integral.

arXiv comment13 pages, 5 figures, 2 tables, 1 appendix

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Cited by in corpus (6)

• Metaplectic geometrical optics for ray-based modeling of caustics: Theory and algorithms
• Quasioptical modeling of wave beams with and without mode conversion: IV. Numerical simulations of waves in dissipative media
• An Assessment Of Full-Wave Effects On Maxwellian Lower-Hybrid Wave Damping
• Demonstration of Metaplectic Geometrical Optics for Reduced Modeling of Plasma Waves
• Collisional whistler instability and electron temperature staircase in inhomogeneous plasma
• Regarding the extension of metaplectic geometrical optics to modelling evanescent waves in ray-tracing codes