Variational Symplectic Particle-in-cell Simulation of Nonlinear Mode Conversion from Extraordinary waves to Bernstein Waves

TL;DR

This paper presents a variational symplectic particle-in-cell simulation method to study nonlinear mode conversion of extraordinary waves to Bernstein waves in magnetized plasmas, revealing significant nonlinear effects on wave behavior.

Contribution

It introduces a long-term accurate symplectic PIC simulation approach for nonlinear wave mode conversion in plasmas, highlighting effects overlooked by previous models.

Findings

Nonlinear effects significantly alter radio-frequency wave physics.

Wave reflectivity and energy deposition evolve notably during conversion.

Even small waves exhibit nonlinear behavior after continuous injection.

Abstract

In this paper, the nonlinear mode conversion of extraordinary waves in nonuniform magnetized plasmas is studied using the variational symplectic particle-in-cell simulation. The accuracy of the nonlinear simulation is guaranteed by the long-term accuracy and conservativeness of the symplectic algorithm. The spectra of the electromagnetic wave, the evolution of the wave reflectivity, the energy deposition profile, and the parameter-dependent properties of radio-frequency waves during the nonlinear mode conversion are investigated. It is illustrated that nonlinear effects significantly modify the physics of the radio-frequency injection in magnetized plasmas. The evolutions of the radio-frequency wave reflectivity and the energy deposition are observed, as well as the self-interaction of the Bernstein waves and mode excitations. Even for waves with small magnitude, nonlinear effects can also become important after continuous wave injections, which are common in the realistic radio-frequency wave heating and current drive experiments.