Low-field peak (LFP) phenomena in helicon plasmas represent an important nonlinear feature in low-magnetic-field helicon discharges and are closely related to wave propagation,reflection, and power coupling processes.Understanding the evolution of wave propagation characteristics under low magnetic field conditions is therefore essential for clarifying the physical mechanism of LFP helicon plasmas.In this work,argon helicon plasmas excited by a single-loop antenna are systematically investigated through numerical simulations using the HELIC code,focusing on the wave propagation and power coupling characteristics in the low magnetic field regime.To quantitatively characterize the propagation state of helicon waves, a multi-parameter standing-wave analysis framework is introduced.The analysis includes the standing wave ratio (SWR), spatial distributions of wave amplitude and phase, amplitude ratios of forward and reflected waves, amplitude and power reflection coefficients, load resistance evolution,radial power deposition, cumulative power distribution, and axial wavenumber power spectra. Based on these diagnostic parameters, the transition of wave propagation from a standing-wave-dominated regime to a traveling-wave-dominated regime is analyzed from the perspectives of spatial field structure, spectral characteristics, and power deposition.The numerical results show that under low magnetic field conditions strong axial reflections lead to pronounced standing-wave structures, resulting in localized power deposition near the antenna region. As the background magnetic field increases, the reflection strength gradually decreases and the propagation state evolves into a traveling-wave-dominated regime. This transition is consistently characterized by the decrease of SWR and reflection coefficients, the reduction of phase discontinuities, and the stabilization of the effective axial wavenumber. Meanwhile, the antenna-plasma coupling strength increases with magnetic field, as indicated by the increase of load resistance. The power deposition pattern also evolves with magnetic field, showing a gradual shift of radial power deposition from the plasma edge toward the core region. In addition, the axial wavenumber power spectrum indicates that the absorbed power becomes increasingly concentrated at lower wavenumbers as the magnetic field increases.These results provide quantitative insights into the wave propagation and power coupling processes in low-magnetic-field helicon discharges and offer useful references for future numerical studies and experimental diagnostics of LFP helicon plasmas.