Laser induced fluorescence measurements of the parallel and perpendicular ion temperatures in a helicon source indicate the existence of a substantial ion temperature anisotropy, T ⊥ /T > 1. The magnitude of the ion temperature anisotropy depends linearly on the source magnetic field. The parallel ion temperature is independent of magnetic field strength while the perpendicular temperature increases linearly with increasing magnetic field. Bohm-like particle confinement is proposed as an explanation for the linear dependence on magnetic field of the perpendicular ion temperature. In the helicon mode, the ion temperature components are independent of RF driving frequency and power and show a trend towards isotropy at high neutral fill pressures.

Abstract. We use data from the Freja satellite to investigate the importance of localized transverse DC electric fields for the generation of broadband waves responsible for ion heating in the auroral region. Theoretical models indicate that shear in the plasma flow perpendicular to the geomagnetic field can generate waves in a broad range around the ion gyrofrequency for parallel currents significantly below the threshold of the current-driven electrostatic ion cyclotron instability. We compare in situ data with laboratory measurements and theoretical predictions, and we find that inhomogeneous electric fields might well be important for the generation of waves in the auroral region.

Recent experiments have demonstrated that ion dominated phenomena, such as the lower hybrid resonance, can play an important role in helicon source operation. In this work, we review recent ion heating measurements and the role of the slow wave in heating ions at the edge of helicon. sources. We also discuss the relationship between parametrically driven waves and ion heating near the rf antenna in helicon sources. Recent measurements of parallel and rotational ion flows in helicon sources have important implications for particle confinement, instability growth, and helicon source operation. In this work we present new measurements of ion flows and summarize the important features of the flows.

Abstract. Space-relevant observational signatures, such as frequency spectra, phase velocities, excitation thresholds, and ion heating, associated with electrostatic ion-cyclotron waves excited by the inhomogeneous energy-density driven (IEDD) instability in a laboratory experiment are presented. A comparison is made between these waves and the broadband ELF waves recently observed in the auroral ionosphere with sounding rockets and satellites. The measurements of broadband spectra, electron-Landau-resonant phase velocities, low excitation threshold value of parallel electron drift speed, and significant perpendicular ion heating suggest that attributing the broadband ELF waves to the IEDD instability mechanism is justified. 14,397

Radial profiles of ion flow vd(r) are measured with laser-induced fluorescence for cases in which the flow direction is parallel (vd>0) and/or antiparallel (vd<0) to the equilibrium magnetic field. Experiments are conducted in the barium-ion plasma of a double-ended Q machine. In cases where the ionizers associated with the two ends are not biased relative to each other, two distinct, counterstreaming ion-beam populations are evident. The insertion of blocking electrodes introduces inhomogeneity into the density profiles of the ion populations without effecting the homogeneity of the radial profile of each population’s drift velocity. In cases where the two ionizers are biased relative to each other, a single ion population exists. Variation in the radial profile of the ion population’s parallel drift velocity vd is produced such that (dvd/dr) can be negative or positive with magnitudes 0–70% of the ion gyrofrequency ωci. These results are discussed in the context of beam-driven and velocity-shear-driven instabilities. Laboratory and space measurements of sheared parallel flow and counterstreaming ion beams are compared.