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Radio Frequency (RF) driven helicon plasma sources are commonly used for their ability to produce high-density argon plasmas (n > 10^19/m^3) at relatively moderate powers (typical RF power < 2 kW). Typical electron temperatures are < 10 eV and typical ion temperatures are < 0.6 eV. A newly designed helicon antenna assembly (with concentric, double-layered, fully liquid-cooled RF-transparent windows) operates in steady-state at RF powers up to 10 kW. We report on the dependence of argon plasma density, electron temperature and ion temperature on RF power. At 10 kW, ion temperatures > 2 eV in argon plasmas are measured with laser induced fluorescence, which is consistent with a simple volume averaged 0-D power balance model. 1-D Monte Carlo simulations of the neutral density profile for these plasma conditions show strong neutral depletion near the core and predict neutral temperatures well above room temperatures. The plasmas created in this high-power helicon source (when light ions are employed) are ideally suited for fusion divertor plasma-material interaction studies and negative ion production for neutral beams., Comment: 12 pages, 19 figues

This is the report on the Workshop on Opportunities, Challenges, and Best Practices for Basic Plasma Science User Facilities, held at the University of Maryland, College Park, MD, on May 20-21, 2019.

Taking advantage of technological developments in wafer-scale processing over the past two decades, such as deep etching, 3-D chip stacking, and double-sided lithography, we have designed and fabricated the key elements of an ultracompact 1.5cm (exp 3)plasma spectrometer that requires only low-voltage power supplies, has no microchannel plates, and has a high aperture area to instrument volume ratio. The initial design of the instrument targets the measurement of charged particles in the 3-20keV range with a highly directional field of view and a 100 duty cycle; i.e., the entire energy range Is continuously measured. In addition to reducing mass, size, and voltage requirements, the new design will affect the manufacturing process of plasma spectrometers, enabling large quantities of identical instruments to be manufactured at low individual unit cost. Such a plasma spectrometer is ideal for heliophysics plasma investigations, particularly for small satellite and multispacecraft missions. Two key elements of the instrument have been fabricated: the collimator and the energy analyzer. An initial collimator transparency of 20 with 3deg x 3deg angular resolution was achieved. The targeted 40 collimator transparency appears readily achievable. The targeted energy analyzer scaling factor of 1875 was achieved; i.e.20 keV electrons were selected for only a 10.7V bias voltage in the energy analyzer.

Ion temperature analysis of the first energetic neutral atom images of the quiet -time, extended magnetosphere provides evidence of multiple regions of ion heating. This study confirms the existence of a dawn -dusk asymmetry in ion temperature predicted for quiescent magnetospheric conditions by Spence and Kivelson (1993) and demonstrates that it is an inherent magnetospheric feature.

Whistler-mode wave emissions are frequently observed at and downstream of interplanetary shocks. Using electron distribution functions measured onboard Ulysses in the energy range 1.6 to 862 eV, we calculate the temperature anisotropy and the wave growth rate of the electromagnetic electron cyclotron instability, Results of the calculations are compared to the whistler wave spectra observed simultaneously. For the studied events there is a good correlation between the wave growth rates and the wave spectra. Particularly, upstream of the shock front where no wave emissions are observed, the anisotropy lies below the wave instability threshold, i.e. the critical anisotropy Ac; on the contrary, downstream of the shock, the anisotropy exceeds Ac in some frequency range. Moreover. the tact that the anisotropy is close to Ac in a large frequency range gives prominence to the effect of velocity space diffusion of the electrons by the waves.

The solar wind is an ionized gas flowing from the solar corona and consisting primarily of free electrons, protons, and doubly-ionized helium. Ulysses solar wind plasma observations through -80.2 degrees solar latitude and continuing equatorward to -40.1 degrees are summarized. Recurrent high-speed streams and corotating interaction regions dominate at mid latitudes. Observation and analysis is given.

During November-December 1991, the International Cometary Explorer (ICE) and Ulysses spacecraft were aligned in solar longitude, with an angular offset as small as 1 deg and a radial offset of 3.8 to 4.0 AU. Both spacecraft carry spectrometers which measure the thermal and suprathermal solar wind electron distributions. During the alignment interval, both spacecraft encountered the declining phase of a high-speed solar wind stream, representing unshocked plasma. We use the aligned observations from ICE and Ulysses to characterized the radial gradients in core and halo electron temperature, relative halo density, and heat flux, as well as the core and total polytropic indices. The thermal properties of the core vary widely in a range from isothermal to adiabatic, while the halo is more nearly isothermal. The halo density falls off more steeply for higher density plasma, and the electron heat flux gradient indicates constant or decreasing distribution skewness.

A previously unidentified type of solar wind forward-reverse shock pair has been observed by Ulysses at 4.64 AU and S32.5 deg. In contrast to most solar wind forward-reverse shock pairs, which are driven by the speed difference between fast solar wind plasma and slower plasma ahead, this particular shock pair was driven purely by the over-expansion of a coronal mass ejection (CME) in transit from the Sun. A simple numerical simulation indicates that the over-expansion was a result of a high initial internal plasma and magnetic field pressure within the CME. The CME observed at 4.64 AU had the internal field structure of a magnetic flux rope. This event was associated with a solar disturbance in which new magnetic loops formed in the corona almost directly beneath Ulysses approximately 11 days earlier. This association suggests that the flux rope was created as a result of reconnection between the 'legs' of neighboring magnetic loops within the rising CME.