Observation of coherent self-organized drift structures in a turbulent DC discharge

It is demonstrated that low-frequency turbulent spectra of a magnetized DC discharge consist of flute-type and drift waves. The existence of waves showing several characteristics of solitons or vortices are made plausible through the properties of propagation and amplitude conditions for self-binding. Self-organized phase-locked waves appear as well as spontaneous transitions to coherent structures at velocities complementary to those of periodic linear modes. Spectra obtained from fluctuations of density and potential only agree for components belonging to periodic drift waves and slow drift soliton-like perturbations. In the regime of turbulence wave coupling occurs, whereas in the windows of order the coherent waves show no coupling with the remaining spectral contributions. The scenario of transition to turbulence is such that, at small magnetic inductions B, waves of short wavelengths establish a regime of order. With increasing B, broad spectra occur with modes of short and long wavelengths. Within this regime of turbulence windows of ordered soliton-like behaviour reappear.