Speaker
Description
Electron and ion transport in non-equilibrium plasmas is inherently complex, exhibiting intricate behavior across both spatial and temporal scales. The Particle-In-Cell (PIC) method is one of the most widely used approaches in plasma physics, as it is the closest to first principles and requires very few input parameters, enabling simulations to self-consistently reach a steady state that closely reflects physical reality. It is well established that satisfying the PIC stability criteria — Δx<λD, Δt < min (0.2 x ωpe-1, Δx /vmax), NPPC sufficiently large — is mandatory to obtain stable and physically meaningful results, where Δx, λD, Δt, ωpe, vmax, and NPPC denote the mesh size, Debye length, time step, plasma frequency, velocity of the fastest macro-particle, and number of macro-particles per cell, respectively.
However, when plasma transport is governed by turbulence or strong instabilities, merely satisfying these criteria at their margins proves insufficient. In this work, we demonstrate that sub-Debye length refinement of the spatial grid combined with high-order shape functions is essential to capture important physical effects and transport mechanisms that are systematically overlooked when first order shape functions with marginally fulfilled PIC criteria are used instead. This finding represents a paradigm shift in quantitative PIC modelling. To support this claim, we compare two typical cases: (i) electropositive, (ii) electronegative plasmas. For both situations, 1D and 2D simulations have been carried out. Remarkable differences occur in the charged particle transport and especially the micro instabilities. In the light of these results, the numerical approach used to simulate plasmas is crucial to capture the anomalous transport.
| Keyword-1 | PIC |
|---|---|
| Keyword-2 | plasma instabilities |