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.

Variations in the plasma parameters of a large volume, helicon source as a function of applied rf power ͑0-2 kW͒, driving frequency ͑8-18 MHz͒, magnetic field ͑0-1.4 kG͒ and fill pressure ͑2-10 mTorr͒ have been studied. The transitions between the capacitive, inductive, and resonant helicon mode are consistent with previous experiments. Our data indicate that the transition to the helicon mode occurs at a unique magnetic field, independent of the driving frequency. Based on the helicon wave dispersion relation, from which helicon wavelengths can be calculated, the observed variations in plasma density as a function of driving frequency suggest that the wavelength of the helicon wave is a weak function of driving frequency. Calculation of the electron energies which correspond to the phase velocity of the driving wave ͑i.e., Landau damping͒ suggest that either Landau damping cannot be responsible for the efficient ionization of helicon sources, or that the helicon portion of the discharge does not extend over the entire radius of the apparatus.

Measurements of parallel and perpendicular ion temperatures in the Large Experiment on Instabilities and Anisotropies ͑LEIA͒ space simulation chamber display an inverse correlation between the upper bound on the ion temperature anisotropy and the parallel ion beta (␤ ϭ8nkT/B 2). Fluctuation measurements indicate the presence of low frequency, transverse, electromagnetic waves with wave numbers and frequencies that are consistent with predictions for Alfvén Ion Cyclotron instabilities. These observations are also consistent with in situ spacecraft measurements in the Earth's magnetosheath and with a theoretical/computational model that predicts that such an upper bound on the ion temperature anisotropy is imposed by scattering from enhanced fluctuations due to growth of the Alfvén ion cyclotron instability.

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We report measurements of electron density and perpendicular ion temperatures in an argon helicon plasma for five different rf antennas: a Nagoya type III antenna, a 'Boswell' saddle coil antenna, a 19 cm long m = +1 helical antenna, a 30 cm long m = +1 helical antenna, and a 19 cm long m = +1 helical antenna with narrow straps. The general properties of the source as a function of rf power and neutral pressure are reviewed and detailed measurements of electron density, electron temperature and ion temperature as a function of magnetic field strength and rf frequency are presented. The experimental results clearly indicate that for all antennas, the electron density is maximized when the rf frequency is close to and just above the lower hybrid frequency. The ion temperature is maximized when the rf frequency is less than 70% of the lower hybrid frequency. Ion temperatures in excess of 1 eV for 750 W of input power have been observed. These results suggest that the mechanisms responsible for coupling energy into the ions and electrons are distinct and therefore helicon sources can be configured to maximize electron density without simultaneously maximizing the perpendicular ion temperature. Enhanced ion heating is not a desirable feature of plasma sources intended for use in plasma etching, thus operational regimes that yield high plasma densities without increased ion heating might be of interest to industry.

Abstract. Initial ENA images obtained with the MENA imager on the IMAGE observatory show that ENAs emanating from Earth's magnetosphere at least crudely track both Dst and Kp. Images obtained during the storm of August 12, 2000, clearly show strong ring current asymmetry during storm main phase and early recovery phase, and a high degree of symmetry during the late recovery phase. Thus, these images establish the existence of both partial and complete ring currents during the same storm. Further, they suggest that ring current loss through the day side magnetopause dominates other loss processes during storm main phase and early recovery phase.

Efficient ion heating in a steady-state helicon plasma source is observed with two external loop antennae just above the ion cyclotron frequency. The ion velocity space distribution is measured by laser induced fluorescence in an argon plasma. The measured bulk ion heating is highly anisotropic ͑the perpendicular temperature increase is ten times the parallel temperature increase͒ even though the plasma is moderately collisional. Measurements of the perturbed distribution function with laser induced fluorescence suggest that an electrostatic ion cyclotron wave is launched.

Laboratory experiments have been conducted to simulate the dynamics of highly localized magnetospheric boundary layers. These regions, such as the plasma sheet boundary layer and the magnetopause, are primary regions of solar wind mass, energy, and momentum transport into the near-Earth space environment. During periods of solar activity, the boundary layers can become compressed to scale lengths less than an ion gyroradius. Theoretical predictions indicate that the plasma can respond to relax these highly stressed conditions through the generation of instabilities in the lower hybrid frequency range. The experiments reported here document the characteristics of waves associated with these instabilities.