Study of similarity rules for electromagnetic process in partially ionized plasmas

TL;DR

This paper investigates the conditions under which electromagnetic processes in partially ionized plasmas exhibit similarity, demonstrating that similarity can be valid in low ionization degree plasmas through theoretical analysis and PIC/MCC simulations.

Contribution

The study introduces the concept of similarity in partially ionized plasmas and proves its validity using PIC/MCC simulations, expanding understanding beyond highly ionized plasmas.

Findings

Similarity in electromagnetic processes is valid for low ionization degree plasmas.

Introduction of neutral molecule density as a new variable enhances similarity conditions.

Simulation results confirm the theoretical analysis of similarity in partially ionized plasmas.

Abstract

As proved by previous study, the similarity of electromagnetic processes in plasmas will be violated by Coulomb collisions between electron and ions. Therefore, there is no similarity in highly ionized collisional plasma. But the situation will be completely different for collisional plasmas with low ionization degree. The main collision type will change from electron-ion Coulomb collision to electron-molecule collision, and a new variable (the number density of neutral molecules) will be introduced into the similarity constraint, which can increase the degree of freedom.Thus, in this condition, the similarity restriction caused by the collision process does not conflict with the other restrictions. Therefore, the similarity for electromagnetic process in collisional plasmas can be valid for partially ionized plasmas. In this paper, we propose the similarity in partially ionized plasmas, and prove it via particle in cell/Monte Carlo (PIC/MCC) simulation. Our research has a wide range of engineering applications.