High order fluid model for streamer discharges: I. Derivation of model and transport data

TL;DR

This paper derives a high order fluid model for streamer discharges using momentum transfer theory, providing detailed transport data and discussing the implementation and accuracy of the model's components in plasma physics applications.

Contribution

It introduces a novel high order fluid model for streamers, derived from the Boltzmann equation, with calculated collision frequencies and transport data for electrons in nitrogen.

Findings

Transport data implementation in streamer models clarified

Assessment of two-term Boltzmann approximation accuracy

Evaluation of mean-energy-dependent collision rates provided

Abstract

Streamer discharges pose basic problems in plasma physics, as they are very transient, far from equilibrium and have high ionization density gradients; they appear in diverse areas of science and technology. The present paper focuses on the derivation of a high order fluid model for streamers. Using momentum transfer theory, the fluid equations are obtained as velocity moments of the Boltzmann equation; they are closed in the local mean energy approximation and coupled to the Poisson equation for the space charge generated electric field. The high order tensor in the energy flux equation is approximated by the product of two lower order moments to close the system. The average collision frequencies for momentum and energy transfer in elastic and inelastic collisions for electrons in molecular nitrogen are calculated from a multi term Boltzmann equation solution. We then discuss, in particular, (1) the correct implementation of transport data in streamer models; (2) the accuracy of the two term approximation for solving Boltzmann's equation in the context of streamer studies; and (3) the evaluation of the mean-energy-dependent collision rates for electrons required as an input in the high order fluid model. In the second paper in this sequence, we will discuss the solutions of the high order fluid model for streamers, based on model and input data derived in the present paper.