WAVELET DENOISING FOR POSTPROCESSING OF A 2D PARTICLE- IN- CELL CODE ∗, ∗∗, ∗∗∗, ∗∗∗∗

Abstract. In this paper, we aim at improving the accuracy of a Vlasov-Poisson solver using a 2D Particle-In-Cell (PIC) scheme, by denoising its charge density field. To this end, we have used an improvement of Donoho and Johnstone’s wavelet denoising technique. To some extent, our work is a continuation of that performed by Chehab et al. [6]. Indeed, they made such a study in the one dimensional case and validated their analysis by considering the simulation of the Landau damping phenomenon. They concluded on the efficiency of the method in reducing the number of particles. However, our approach is quite different, since we do not use wavelets to directly interpolate the charge density, but we smooth the density field calculated by the PIC code. This is carried out via an iterative wavelet denoising technique introduced by Azzalini et al. [2]. Our work consists in studying the application of the method as a post-processing tool, in view of a future embedding into the PIC code. The results are the following: first, we showed that the hypotheses underlying the application of this method are valid. Secondly, we can infer from this study that it is possible to significantly reduce the amount of data needed for a simulation. Résumé. L’objectif de ces travaux est d’accrôıtre la précision d’un solveur Vlasov-Poisson base ́ sur un schéma de type Particle-In-Cell (PIC). Pour ce faire, a ̀ l’instar de Chehab et coll. [6], nous avon