Initial results of the Pioneer 8 VLF Electric Field Experiment

The Pioneer 8 spacecraft was launched into an outbound heliocentric orbit on December 13, 1967. The payload includes a simple VLF electric field detector that uses the 423-MHz antenna supplied for the Stanford radio propagation experiment. Broadband signals in the frequency range 0.1–100 kHz are examined by performing a pulse height analysis of the waveform, and wave amplitudes are also measured in bandpass channels centered at 0.4 and 22 kHz. It is found that low-frequency electric field oscillations can always be detected in the solar wind, and that the amplitudes vary with changing interplanetary conditions. Large amplitude high-frequency noise bursts are also detected sporadically, and we identify these as electron plasma oscillations in the solar wind.