Learning collision operators from plasma phase space data using differentiable simulators
This work addresses the challenge of modeling collisional dynamics in plasmas for researchers in computational physics, offering a computational efficient approach, though it is incremental as it builds on existing differentiable simulation techniques.
The authors tackled the problem of inferring collision operators from plasma phase space data by proposing a method that combines a differentiable kinetic simulator with gradient-based optimization, demonstrating that the learned operators are more accurate than particle-track estimates and agree with theoretical predictions.
We propose a methodology to infer collision operators from phase space data of plasma dynamics. Our approach combines a differentiable kinetic simulator, whose core component in this work is a differentiable Fokker-Planck solver, with a gradient-based optimisation method to learn the collisional operators that best describe the phase space dynamics. We test our method using data from two-dimensional Particle-in-Cell simulations of spatially uniform thermal plasmas, and learn the collision operator that captures the self-consistent electromagnetic interaction between finite-size charged particles over a wide variety of simulation parameters. We demonstrate that the learned operators are more accurate than alternative estimates based on particle tracks, while making no prior assumptions about the relevant time-scales of the processes and significantly reducing memory requirements. We find that the retrieved operators, obtained in the non-relativistic regime, are in excellent agreement with theoretical predictions derived for electrostatic scenarios. Our results show that differentiable simulators offer a powerful and computational efficient approach to infer novel operators for a wide rage of problems, such as electromagnetically dominated collisional dynamics and stochastic wave-particle interactions.