Self-organized pattern formations through double layers in different negative differential regimes

Abstract

Self-organized patterns (SOPs) are observed to develop in a glow discharge regime using a novel plasma source consisting of asymmetric electrodes and a controlling biased grid. The plasma is generated in two distinctly different glow discharge regimes while triggering instability through sheath-plasma interactions, in the absence of any additional constraints like magnetic or electric fields. In line with our earlier report [Debnath et al., Phys. Plasmas 32, 043507 (2025)], this study further advances the investigation on formations of SOPs with a focus on complex structure formations around the anode in the higher discharge regime, facilitating the negative differential resistance (NDR) phenomenon during glow discharge in a hollow cathode system. Following the space charge effect, SOPs form between double layers (DLs), which act as walls or boundaries for pattern confinement. In the higher discharge regime, nonlinear analysis like the autocorrelation and Hurst coefficient displays a clear transition of chaotic to periodic behavior, supporting the long-range correlation and suggesting the formation of SOPs. The critical transition in the dynamics of the system also led to the presence of streaming instabilities in the present investigation. The Poincaré plots depict the transition of the system from chaotic fluctuation to an ordered state, creating bunches of streaming electrons. So, all of these potential boundary conditions, streaming plasma instability, simultaneous nonlinear sheath-plasma interactions, and NDR, collectively result in conducive conditions for the formation of DLs near the anode surface, leading to the generation of SOPs during the present operational regime.