Chorus‐related electrostatic bursts at Jupiter and Saturn

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Abstract
Analyses of the wide band plasma wave data obtained by Voyager 1 and 2 at Jupiter and Saturn have revealed electrostatic bursts similar to those recently discovered at earth in association with whistler mode chorus. In all three magnetospheres the bursts are characterized by sporadic emissions near or slightly below the electron plasma frequency with bandwidths ranging from 10% to more than 50% of the center frequency. The events found at Jupiter occur in the middle magnetosphere during both the dayside as well as the early morning passes. At Saturn the bursts occurred in the outer regions of the magnetosphere during the dayside pass. In each of the events analyzed, evidence exists for modulation of the electrostatic bursts by a low‐frequency wave, presumably chorus. One of the observations gained at Jupiter includes the detection of a low‐frequency band at the proper frequency for chorus. Detailed waveform analysis confirms that this band does, indeed, modulate the electrostatic bursts. On the basis of the present understanding of the terrestrial observations, it is believed that the electrostatic bursts are generated by an electron beam trapped in Landau resonance with the chorus.