Radio Jupiter after Voyager: An overview of the planetary radio astronomy observations

We present an overview of Jupiter's low‐frequency radio emission morphology as observed by the planetary radio astronomy (PRA) instrument onboard the Voyager spacecraft. The PRA measurement capabilities and limitations are summarized following over two years of experience with the instrument. As a direct consequence of the PRA spacecraft observations, unprecedented in terms of their sensitivity and frequency coverage, at least three previously‐unrecognized emission components have been discovered: broadband and narrow‐band kilometric emission and the lesser‐arc decametric emission. Their properties are reviewed here. In addition, the fundamental structure of the decameter wavelength and hectometer wavelength emission, which is now believed to be almost exclusively in the form of complex but repeating arc structures in the frequencytime domain, is described here for the first time. Dramatic changes in the emission morphology of some components as a function of the sun‐Jupiter‐spacecraft angle (local time) are described. Finally, the PRA in situ measurements of the Io plasma torus hot‐to‐cold electron density and temperature ratios are summarized.