The intense broadband electrostatic turbulence detected in the near vicinity of the shuttle during the OSS 1 and Spacelab 2 missions is interpreted in terms of the excitation of the beam‐arc plasma instability. This new instability is driven by the free energy involving the interaction of the beam‐arc (asymmetric ring) distribution function of the pickup water ions with the background ionospheric plasma. The results of a linear analysis show that the beam‐arc plasma instability has unique characteristics that can explain most details of the wave spectrum detected with the Plasma Diagnostic Package (PDP) within 10 m of the shuttle. However, an analysis on the effects of varying beam‐arc parameters such as the angular dependence and thermal spread shows that the spectrum peak near the lower hybrid frequency (ΩLH) is likely to be a result of nonlinear effects. This is because the heating of beam‐arc ions expected in the nonlinear regime should lead to a resonant type instability which according to linear theory does not involve significant growth near ΩLH. The linear beam‐arc plasma instability theory can also explain the enhancements of the low‐frequency component of the spectrum observed during water dumps. These enhancements are interpreted in terms of beam‐arc plasma waves propagating in directions which are consistent with the highly inhomogeneous characteristics of the water dump regions.

Data from the Shuttle Potential and Return Electron Experiment (SPREE) flown as part of the Tethered Satellite System (TSS 1) are used to determine the detailed characteristics of beam arc distributions of pickup ions due to molecules outgassed or ejected from the shuttle. These ion distributions are only detected near the plane perpendicular to the magnetic field direction in an angular range of ±45° about the minimum angle to ram. Their flux is largest when the angle between this plane and the shuttle ram direction is smallest. Generally, ion spectra peak in the range 19 to 25 eV at the minimum angle between the perpendicular plane and the ram direction. The peak energy decreases smoothly as this angle increases. Weak fluxes are measured above the peak, to energies as high as 150 eV. Within the SPREE energy range, two‐dimensional distribution functions of beam arc ions in the perpendicular plane have teardrop shapes, symmetric about the minimum angle to shuttle ram with deep minima in the centers. Variations in the peak energies of differential number fluxes agree with collisionless trajectory analysis, assuming that the ions are H2O+ and allowing for different initial velocities before charge exchange. The lowest densities for beam arc ions occur during periods of purely residual outgassing from the shuttle. Ion densities increase by a factor of 5 during waste water dumps. The highest densities occur during operation of the flash evaporator system when the pickup ion densities in daylight can exceed 105 ions cm−3, about 30% of the estimated ambient plasma density. We also present a nonlinear numerical analysis to study the stability of beam arc generated plasma waves and explain electrostatic spectra measured during previous shuttle flights.

The combined operation of an HF or MF ground transmitter and a VLF transmitter for enhanced ionospheric heating is discussed. The HF or MF transmitter, operated in a pulsed mode, can preferentially produce short-scale density striations that can render the nonlinear mode conversion of the subsequently launched VLF waves into lower hybrid waves. In addition to the mode conversion process, the VLF waves, if intense enough, can also excite meter-scale density striations and lower hybrid waves via parametric instabilities. Intensified density striations and enhanced airglow are expected, and they can be detected by incoherent backscatter radars and photometers, respectively. The feasibility and planning of the proposed experiments are addressed.

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