Observations of a structure-forming instability in a dc-glow-discharge dusty plasma

By adjusting the anode current and axial magnetic strength of a dc-glow-discharge dusty plasma, we have found plasma and dust conditions conducive to dusty plasma structurization, similar to the one discussed theoretically by Morfill and Tsytovich [Plasma Phys. Rep. 26, 682 (2000)]. The structurization instability leads to the formation of a pattern where the dust suspension transforms into alternating stationary regions of high and low dust densities. We have measured the dependence of the wavelength of the nonpropagating dust density structures on neutral pressure and plasma density and discussed the results in terms of the dispersion relation obtained by D'Angelo [Phys. Plasmas 5, 3155 (1998)] for an ionization and ion-drag instability. The observations are also considered in light of a recent theoretical prediction by Khrapak et al. [Phys. Rev. Lett. 102, 245004 (2009)] that under certain conditions the effects of the polarization force on dust particles can cause dust acoustic waves to stop propagating, resulting in the formation of aperiodic, stationary dust density structures.