INTERSTELLAR PICKUP H-AU - PIONEER-10 PLASMA AND MAGNETIC-FIELD ANALYSES( IONS AT 8.3)

Analysis of Pioneer 10 plasma and magnetic field observations at 8.3 A U in 1975 provides new evidence for the presence of interstellar picku p hydrogen (H+) ions. Use of plasma sensors that look far from the sol ar wind direction confirms the spherical shell distribution of the pic kup ions in velocity space. Phase space density and flux estimates are closely consistent with those from Ulysses measured under similar con ditions. Power spectral analyses of the magnetic field data show a dis tinct signal a little above the proton gyrofrequency, consistent with the presence of Doppler-shifted ion-cyclotron waves generated by H+ pi ckup ions. These results show that the Pioneer data set has the potent ial for systematic studies of the global properties of interstellar pi ckup ions.