We extend the previous studies of intense hydromagnetic waves at Giacobini-Zinner to investigate the mode and direction of wave propagation. Simultaneous high-resolution measurements of electron density fluctuations demonstrate that the long period (approx.100 s) waves are propagating in the magnetosonic mode. Principal axis analyses of the long period waves and accompanying partial rotations show that the sum of the wave phase rotations is 360/sup 0/C, indicating that both are parts of the same wave oscillation. From the time sequence of the steepened waveforms observed by ICE, we demonstrate that the waves must propagate towards the sun with C/sub ph/ < V/sub sw/. All available observations are consistent with wave generation by the resonant ion ring or ion beam instability which predicts right-hand polarized waves propagating in the ion beam (solar) direction. The large amplitudes ..delta.. polarized B/absolute value of Bapprox.0(1) and small scale sizes (rotational discontinuities) of the cometary waves suggest that rapid pitch-angle scattering and energy transfer with energetic ions should occur. Since the waves are highly compressive, ..delta.. absolute value of B/absolute value of B = 0(0.5), one can also anticipate first-order Fermi acceleration. 15 refs., 6 figs.

On September 11, 1985 the International Cometary Explorer passed behind Comet Giacobini-Zinner with a closest approach distance of 7800 km. In agreement with Alfven's interplanetary magnetic field line draping model of cometary type I tails, a well defined 1 x 10/sup 4/ km diameter magnetotail was observed downstream of the inner coma. This study uses the ICE magnetic field, plasma electron, plasma wave, and energetic ion observations to investigate the structure and stability of the Giacobini-Zinner magnetic tail. Emphasis is placed on the identification of differences and similarities between cometary and planetary magnetotails. Finally, the ICE magnetotail observations are discussed in relation to the global solar wind interaction with P/Giacobini-Zinner. 33 refs., 8 figs.

Utilizing the electron and magnetic field data from the ICE tail traversal of Comet Giacobini-Zinner along with the MHD equations, we have developed a steady state, stress balance model of the cometary magnetotail. With it we infer many important but unmeasured ion properties within the G-Z magnetotail both at ICE and upstream at the average point along each streamline where cometary ions are picked-up. The derived tailward ion flow speed at ICE is quite constant at approx.-20 to -30 km/sec across the entire tail. The flow velocity, ion temperature, density, and ion source rates upstream from the lobes (current sheet) at the average pickup locations are approx.-75 km/sec (approx.-12), approx.4 x 10/sup 6/ K (approx.1 x 10/sup 5/), approx.20 /cm/sup 3/ (approx.400), and approx..15 /cm/sup 3//sec (approx.3.6). Gradients in the plasma properties between these two regions are quire strong. Implications of our inferred plasma properties for the near-nucleus region and for cometary magnetotail formation are examined. 9 refs., 1 fig.

Spectral analyses of the high resolution magnetic field data are employed to determine if there is evidence of cometary heavy ion pickup when ICE was closest to Halley, approx.28 x 10/sup 6/ km. No evidence is found for the presence of heavy ion cyclotron waves. However, from this search, two new wave modes are discovered in the solar wind: electromagnetic ion cyclotron waves and drift mirror mode waves. Both modes have scales of 10 to 60 s (1 to 6 T/sub p/) in the spacecraft frame. The possibility of wave generation by cometary hydrogen pickup is explored. Theoretical arguments and further experimental evidence indicates that cometary origin is improbable. The most likely source is plasma instabilities associated with solar wind stream-stream interactions. VLF electrostatic emissions are found to occur in field minima or at gradients of the drift mirror structures. Possible generation mechanisms of drift mirror mode waves, cyclotron waves and electrostatic waves are discussed.

This document addresses basic configurational tradeoffs associated with the SP-100 class of nuclear space power systems. In the SP-100 project, the three reference designs, fallback, baseline, and advanced, employ thermoelectric power conversion with different thermoelectric materials. This issue of the document presents results generated for the thermoelectric design as of the end of 1985. Emphasis is placed on showing general trends and the range of possibilities that could result from selection of a particular design. This document, which reflects efforts on 100-kWe reference designs as of the end of 1985, will be extended and updated to reflect progress in the design studies of the follow-on ground engineering phase for which a 300-kWe size has been selected. THere is a considerable flexibility to the SP-100 power system so that it will generally be most advantageous to tailor it to meet user requirements.

This report contains a discussion on many aspects of a nuclear electric propulsion planetary science mission and spacecraft using the proposed SP-100 nuclear power subsystem. A review of the science rationale for such missions is included. A summary of eleven nuclear electric propulsion planetary missions is presented. A conceptual science payload, mission design, and spacecraft design is included for the Saturn Ring Rendezvous mission. Spacecraft and mission costs have been estimated for two potential sequences of nuclear electric propulsion planetary missions. The integration issues and requirements on the proposed SP-100 power subsystems are identified.