A 3-DIMENSIONAL PLASMA AND ENERGETIC PARTICLE INVESTIGATION FOR THE WIND SPACECRAFT

This instrument is designed to make measurements of the full three-dim ensional distribution of suprathermal electrons and ions from solar wi nd plasma to low energy cosmic rays, with high sensitivity, wide dynam ic range, good energy and angular resolution, and high time resolution . The primary scientific goals are to explore the suprathermal particl e population between the solar wind and low energy cosmic rays, to stu dy particle acceleration and transport and wave-particle interactions, and to monitor particle input to and output from the Earth's magnetos phere. Three arrays, each consisting of a pair of double-ended semi-co nductor telescopes each with two or three closely sandwiched passivate d ion implanted silicon detectors, measure electrons and ions above si milar to 20 keV. One side of each telescope is covered with a thin foi l which absorbs ions below 400 keV, while on the other side the incomi ng <400 keV electrons are swept away by a magnet so electrons and ions are cleanly separated. Higher energy electrons (up to similar to 1 Me V) and ions (up to 11 MeV) are identified by the two double-ended tele scopes which have a third detector. The telescopes provide energy reso lution of Delta E/E approximate to 0.3 and angular resolution of 22.5 degrees x 36 degrees, and full 4 pi steradian coverage in one spin (3 s). Top-hat symmetrical spherical section electrostatic analyzers with microchannel plate detectors are used to measure ions and electrons f rom similar to 3 eV to 30 keV. All these analyzers have either 180 deg rees or 360 degrees fields of view in a plane, Delta E/E approximate t o 0.2, and angular resolution varying from 5.6 degrees (near the eclip tic) to 22.5 degrees. Full 4 pi steradian coverage can be obtained in one-half or one spin. A large and a small geometric factor analyzer me asure ions over the wide flux range from quiet-time suprathermal level s to intense solar wind fluxes. Similarly two analyzers are used to co ver the wide range of electron fluxes. Moments of the electron and ion distributions are computed on board. In addition, a Fast Particle Cor relator combines electron data from the high sensitivity electron anal yzer with plasma wave data from the WAVE experiment (Bougeret et al., in this volume) to study wave-particle interactions on fast time scale s. The large geometric factor electron analyzer has electrostatic defl ectors to steer the field of view and follow the magnetic field to enh ance the correlation measurements.