Nonlinear evolution of the modified Simon-Hoh instability via a cascade of sideband instabilities in a weak beam plasma system

Wave-driven electron inward transport in a magnetic nozzle

Plasma flows in divergent magnetic fields resembling a magnetic nozzle can be found over wide scales ranging from astrophysical objects to terrestrial plasma devices. Plasma detachment from a magnetic nozzle is a frequent occurrence in natural plasmas, e.g., plasma ejection from the Sun and release from the Sun's magnetic field, forming the solar wind. Plasma detachment has also been a challenging problem relating to space propulsion devices utilizing a magnetic nozzle, especially the detachment of the magnetized electrons having a gyro-radius smaller than the system's scale is required to maintain zero net current exhausted from the system. Here we experimentally demonstrate that a cross-field transport of the electrons toward the main nozzle axis, which contributes to neutralizing the ions detached from the nozzle, is induced by the spontaneously excited magnetosonic wave having the frequency considerably higher than the ion cyclotron frequency and close to the lower hybrid frequency, driving an E × B drift that only effects the electrons. Wave-induced transport and loss have been one of many important issues in plasma physics over the past several decades. Conversely, the presently observed electron inward transport has a beneficial effect on the detachment by reducing the divergence of the expanding plasma beam; this finding will open a new perspective for the role of waves and instabilities in plasmas.

Self-Organization, Structures, and Anomalous Transport in Turbulent Partially Magnetized Plasmas with Crossed Electric and Magnetic Fields

Self-organization and anomalous transport in gradient-drift driven turbulence in partially magnetized plasmas with crossed electric and magnetic fields is demonstrated in two-dimensional fluid simulations. The development of large scale structures and flows is shown to occur as a result of the inverse energy cascade from short wavelength instabilities. The turbulence shows complex interaction of small scale modes with large scale zonal flow modes, vortices, and streamers resulting in strongly intermittent anomalous transport that significantly exceeds the classical collisional values. The turbulence driven secondary instabilities and large scale structures are shown to dominate the anomalous electron current. Such anomalous transport and structures are consistent with a number of experimental observations in laboratory plasmas.

Rotating instability in low-temperature magnetized plasmas

The formation of a rotating instability associated with an ionization front ("rotating spoke") and driven by a cross-field current in a cylindrical magnetized plasma is shown and explained for the first time on the basis of a fully kinetic simulation. The rotating spoke is a strong double layer (electrostatic sheath) moving towards the higher potential region at a velocity close to the critical ionization velocity, a concept proposed by Alfvén in the context of the formation of the solar system. The mechanisms of cross-field electron transport induced by this instability are analyzed.