Spatiotemporal signatures of periodic pulling during ionization-wave-mode transitions

Abstract

Using measurements of spatiotemporal patterns in the light-emission fluctuations of the positive column of a neon glow discharge, the spatiotemporal nature of the nonlinear interaction, known as periodic pulling, which occurs between pairs of self-excited, propagating, ionization waves, is characterized. Transitions occur between discrete longitudinal ionization-wave modes if the discharge current is smoothly ramped. At a given discharge current, multiple modes coexist along the entire plasma column with one mode dominating over all others. As the current is incremented towards the transition from one dominant mode to another, the prospective dominant mode grows and interacts with the dominant mode in space and time. Spatiotemporal periodic pulling is experimentally demonstrated. Characteristic modulation in both time and space of both frequency and wave-number spectra are presented. This phase modulation is low frequency and long wavelength. It maximizes at the instant of transition when both modes are of comparable amplitudes. The transition involves an Eckhaus instability that triggers the spatiotemporal dislocation, which represents the creation or annihilation of a mode number.

Self-Consistent Analysis of the Spatial Relaxation of a Disturbed Neon Glow Discharge

“…In the downstream region, a spatiotemporal evolution occurs which is similar to that observed in ionization waves. (1,43) The movement of the spatial relaxation structure in cathode direction corresponds to the negative phase velocity typical of ionization waves. A similar spatiotemporal evolution is found when analysing other macroscopic quantities, such as the electric field strength and the electron density.…”

Hysteresis of ionization waves

“…These measurements were taken due to the model predictions described later. Side-bands were also identified to play an important role in the transition process [18,19]: It was experimentally proven that the mode transition is a non-linear process in which a long-wavelength instability (Eckhaus instability) provides an energy transfer from the initial to the final wave mode. This process may be described as a spatio-temporal periodic pulling process.…”

Nonlinear interaction of drift waves with driven plasma currents

“…For larger frequency mismatches phase slippage occurs more frequently. The phase slippage and the broadening of the peak are evidence for incomplete synchronization and periodic pulling [10,14,[21][22][23].…”