Magnetized plasma pressure filaments: Analysis of chaotic and intermittent transport events driven by drift-Alfvén modes

Abstract

The origin of intermittent fluctuations in an experiment involving several interacting electron plasma pressure filaments in close proximity, embedded in a large linear magnetized plasma device, is investigated. The probability density functions of the fluctuations on the inner and outer gradient of the filament bundle are non-Gaussian and the time series contain uncorrelated Lorentzian pulses that give the frequency power spectral densities an exponential shape. A cross-conditionally averaged spatial reconstruction of a temporal event reveals that the intermittent character is caused by radially and azimuthally propagating turbulent structures with transverse spatial scales on the order of the electron skin depth. These eruption events originate from interacting pressure gradient-driven drift-Alfvén instabilities on the outer gradient and edge of the filament bundle. The temporal Lorentzian shape of the intermittent structures and exponential spectra are suggestive of deterministic chaos in the underlying dynamics; this conclusion is supported by the complexity–entropy analysis (CH-plane) that shows the experimental time series are located in the chaotic regime.

Emissive cathode immersed in a plasma: plasma–cathode interactions, operation and stability

“…For instance, the Big Red Ball [35] and the Plasma Couette eXperiment [36] at the University of Wisconsin implement the interaction of large current injection from emissive cathodes with large-scale or multipolar magnetic fields to study laboratory astrophysical relevant phenomena such as the dynamo instability, the magnetorotational instability or the dynamic of the Parker spiral in the solar wind [37]. Hot emissive cathodes immersed in a preexisting plasma also shed new light on transport and plasma turbulence in magnetized plasma columns [38,39], plasma flow generation [40,41], or the dynamic of interacting plasma filaments [42,43]. The control of electric fields perpendicular to the ambient magnetic field is also crucial for a number of applications of E × B configurations [44], and among them, high-throughput plasma mass separation [45,46].…”