The spinning terrella plasma experiment: Initial results

Abstract

The observation of 40 keV field-aligned plasma flows (Sheldon et al., 1998) has been conjectured as the result of a space-charge driven instability generating kV parallel potentials (Sheldon, 1999), which occur whenever hot plasma drifts in an inhomogeneous magnetic field. Such conditions occur in almost any magnetic field that interacts with an energetic plasma: at the Earth, the Sun, Jupiter, and perhaps even astrophysical magnetospheres of stars, black holes and active galactic nuclei, all of which possess collimated flows. From this ubiquity, field-aligned flows were looked for in a table top plasma experiment involving a permanent magnet and a direct current (dc) discharge source of energetic plasma. It is emphasized that a one-fluid plasma theory such as magnetohydrodynamics is incapable of describing a parallel potential drop, and that most second-order corrections to the theory predict weak parallel voltages proportional to the thermal energy. In contrast, it is shown photographs of the plasma and peculiar high-voltage (500 eV≫kT) discharges suggestive of a large field-aligned potential drop. It is proposed that this may be a manifestation of the quasi-neutral catastrophe heretofore neglected by space and laboratory plasma physicists, which may unify many disparate observations.