Validation of a reacting three-fluid 5-moment model for THz breakdown

High powered THz waves have potential applications in scanning, remote sensing, and high-data rate communication. At sufficiently high power ionization of the surrounding gas is inevitable, leading to absorption, refraction, and reflection of the THz waves. Understanding the plasma's formation, as well its interaction with the EM fields, is necessary to the design of high powered THz devices. Self-consistent modeling of THz breakdown is challenging as it covers many orders of magnitude in speed (light speed to the neutral thermal speed) and ionization fraction (neutral gas to near full ionization). In prior research, fluid models in the drift-diffusion approximation have found qualitative agreement with experiments for a 110 GHz plasma. In order to achieve better quantitative agreement gas heating, plasma chemistry, and reaction rates that account for steep gradients in density and temperatures will be needed. In this work, an existing three-species (electron-ion-neutral atom) 5-moment model developed by Meier and Shumlak [Physics of Plasmas, 19, 7, (2012)] is extended to include physically motivated non-Maxwellian local electron distributions in reaction rate calculations. Initial results and model validation are presented for THz breakdown in atmospheric argon.