Negative streamer fronts: comparison of particle and fluid models and hybrid coupling in space

摘要

To understand ionization fronts and the growth of streamer channels, both fluid and particle modelshave been developed. While fluid models are computationally efficient in regions with large particledensities like the interior of a streamer finger, particle models represent the full microscopic scatteringphysics and are appropriate for regions with low densities and for particles with high energies like inthe 'pulled' ionization front ahead of the streamer finger. Furthermore, the statistics of few singleparticles in the front can create fluctuations of velocity and ionization rate and might trigger inherentinstabilities. The goal of the project is therefore to develop a computation scheme that is hybrid inspace. Here, we compare planar ionization fronts in the fluid or the particle model. The ionizationdensity behind the particle front is higher while front velocities are similar. We analyze and explainthis discrepancy. We also sketch the concept of hybrid model coupling of different spatial regions.