Revealing the transient ionization dynamics and mode-coupling mechanisms of helicon discharge through a self-consistent multiphysics model

Helicon plasma sources play a central role in applications ranging from material treatment to space propulsion and fusion, yet the physical processes governing their ignition and transient ionization remain incompletely understood. Here we develop a self-consistent, fully coupled multiphysics framework implemented in COMSOL Multiphysics, that integrates Maxwell's equations, electron energy transport, drift-diffusion kinetics, and heavy-species chemistry to capture the complete spatiotemporal evolution of helicon discharges. The model reproduces experimental measurements across pressure, magnetic field, and frequency ranges, and reveals a previously unresolved transient ionization stage characterized by a rapid density rise within ~ 10- 4 s, accompanied by a two-peak electron temperature structure that governs the formation of the dense plasma core. By tracking the RF power flow and field topology, we characterize the transient redistribution of RF energy during ignition. A short-lived phase of localized energy deposition accompanies the onset of ionization, followed by a gradual restructuring of the RF field distribution as the plasma density increases, together with rapid density growth and profile restructuring. Systematic parametric scans further reveal the sensitivity of this mode-coupling process to gas pressure, magnetic field strength, and driving frequency. These results provide a unified picture of the ignition in helicon plasmas and establish a predictive tool for the design and optimization of RF plasma sources across space propulsion, manufacturing, and fusion technologies.