Measurements of plasma wave spectra in Jupiter's magnetosphere

Abstract

The Voyager 1 and 2 plasma wave instruments had to be designed without direct knowledge of the intensities or spectral characteristics of waves in Jupiter's magnetosphere, the possible environmental problems at Jupiter, or the possible in‐flight interference effects from Voyager subsystems. The wave instruments operated continuously during the 1979 Voyager encounters, and now we can assess in detail the performance of the receiver/spacecraft system within the magnetosphere of Jupiter. We present compressed plots of E field averages for all of the 16‐channel spectrum analyzer data from the Voyager 1 and 2 magnetosphere traversals to provide an overall framework for the discussion. We illustrate the importance of considering peaks as well as averages by using 16‐channel measurements from the first inbound and last outbound bow shock for Voyager 2. We also present selected wideband measurements from the waveform receivers to demonstrate how many important wave bursts are variable in times less than or comparable to the 4‐s scan period of the 16‐channel analyzer. These signal characteristics could not be determined by using the 16‐channel analyzer data alone. In addition, we show how the continuous frequency coverage of the waveform data link provides extremely valuable information on the complex spectra of Jovian plasma waves. These wideband frames also lead to the identification of significant variable interference effects associated with the changing interaction between spacecraft subsystems and the Jupiter plasma environment.