Electron neural closure for turbulent magnetosheath simulations: energy channels
This work addresses the challenge of accurately simulating energy channels in turbulent plasmas for space physics applications, representing an incremental improvement over existing methods.
The authors tackled the problem of modeling electron pressure in turbulent magnetosheath simulations by introducing a non-local five-moment electron pressure tensor closure using a Fully Convolutional Neural Network, which significantly outperformed local closures like MLP or double adiabatic expressions in reconstructing pressure-strain interactions.
In this work, we introduce a non-local five-moment electron pressure tensor closure parametrized by a Fully Convolutional Neural Network (FCNN). Electron pressure plays an important role in generalized Ohm's law, competing with electron inertia. This model is used in the development of a surrogate model for a fully kinetic energy-conserving semi-implicit Particle-in-Cell simulation of decaying magnetosheath turbulence. We achieve this by training FCNN on a representative set of simulations with a smaller number of particles per cell and showing that our results generalise to a simulation with a large number of particles per cell. We evaluate the statistical properties of the learned equation of state, with a focus on pressure-strain interaction, which is crucial for understanding energy channels in turbulent plasmas. The resulting equation of state learned via FCNN significantly outperforms local closures, such as those learned by Multi-Layer Perceptron (MLP) or double adiabatic expressions. We report that the overall spatial distribution of pressure-strain and its conditional averages are reconstructed well. However, some small-scale features are missed, especially for the off-diagonal components of the pressure tensor. Nevertheless, the results are substantially improved with more training data, indicating favorable scaling and potential for improvement, which will be addressed in future work.