A comparison of 3D particle, fluid and hybrid simulations for negative streamers

TL;DR

This paper compares 3D particle, fluid, and hybrid simulation models for negative streamers, highlighting their accuracy and computational efficiency in capturing electron dynamics and streamer branching.

Contribution

It introduces a validated 3D hybrid model coupling particle and fluid approaches, improving simulation accuracy while maintaining efficiency.

Findings

The hybrid model closely matches the particle model in negative streamer simulations.

The extended fluid model approximates particle and hybrid models well until stochastic effects dominate.

The classical fluid model underestimates streamer velocities and ionization densities.

Abstract

In the high field region at the head of a discharge streamer, the electron energy distribution develops a long tail. In negative streamers, these electrons can run away and contribute to energetic processes such as terrestrial gamma-ray and electron flashes. Moreover, electron density fluctuations can accelerate streamer branching. To track energies and locations of single electrons in relevant regions, we have developed a 3D hybrid model that couples a particle model in the region of high fields and low electron densities with a fluid model in the rest of the domain. Here we validate our 3D hybrid model on a 3D (super-)particle model for negative streamers in overvolted gaps, and we show that it almost reaches the computational efficiency of a 3D fluid model. We also show that the extended fluid model approximates the particle and the hybrid model well until stochastic fluctuations become important, while the classical fluid model underestimates velocities and ionization densities. We compare density fluctuations and the onset of branching between the models, and we compare the front velocities with an analytical approximation.