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The ring plane event detected by the Voyager 1 and 2 Planetary Radio Astronomy experiment is distinct from Saturn kilometric radiation (SKR) and from Saturn electrostatic discharges (SED). It consists of radio noises recorded only during Saturnian ring plane crossings. Several models are tested. The electrostatic noise on the antennas resulting from the passage of electrons and ions near the antennas (quasi‐thermal noise) leads to order of magnitude much lower than the observed values. Shot noise due to electrons and ions collected and/or emitted by the antennas and spacecraft can explain the noise recorded during Saturn Voyager 1 ring plane crossing and partly what is observed in the case of Voyager 2. For this latter event we must introduce the shot noise due to grain impacts. A quantitative approach of this process gives an estimation of the dust size ∼ 2.3 µm just outside the G‐ring.

Within distances to Uranus of about 6 x 10(6) kilometers (inbound) and 35 x 10(6) kilometers (outbound), the planetary radio astronomy experiment aboard Voyager 2 detected a wide variety of radio emissions. The emission was modulated in a period of 17.24 +/- 0.01 hours, which is identified as the rotation period of Uranus' magnetic field. Of the two poles where the axis of the off-center magnetic dipole (measured by the magnetometer experiment aboard Voyager 2) meets the planetary surface, the one closer to dipole center is now located on the nightside of the planet. The radio emission generally had maximum power and bandwidth when this pole was tipped toward the spacecraft. When the spacecraft entered the nightside hemisphere, which contains the stronger surface magnetic pole, the bandwidth increased dramatically and thereafter remained large. Dynamically evolving radio events of various kinds embedded in these emissions suggest a Uranian magnetosphere rich in magnetohydrodynamic phenomena.

16. We thank the entire Voyager team at NASA Headquarters and the Jet Propulsion Laboratory (JPL) for their support. We are especially grateful to R. Poynter for his invaluable assistance and support. We also thank E. Miner and J. Diner for their efforts to arrange the wideband coverage; J. Anderson, P. Jepsen, and G. Garneau for their assistance with the wideband data processing; C. Stembridge for his help in solving numerous problems; H. Bridge, J. Belcher, J. Scudder, and N. Ness for providing data in advance of publication and for their helpful discussions; and R. Anderson, R. West, L. Granroth, and R. Brechwald for carrying out the data reduction. The research at the University of Iowa was supported by NASA through contract 954013 with JPL, through grants NGL-16-001-002 and NGL-16-001-043 from NASA Headquarters, and by the Office of Naval Research. The research at TRW was supported by NASA through contract 954012 with JPL.

During the Uranus ring plane crossing at 4.57 Uranus radii, the PRA instrument aboard Voyager 2 recorded a characteristic intense noise extending 104 km perpendicular to the ring plane. This is interpreted as due to impact ionization of dust grains striking the spacecraft. The noise level is smaller by a factor ∼ 170 than the same kind of event recorded during Voyager 2 Saturn encounter just outside the G‐ring. The results indicate a maximum concentration of about 10−9 cm−3 of grains larger than 1 µm with a scale height ∼ 150 km across the ring plane. The distribution is asymmetrical, extending farther on the sunlit side. The inferred geometric optical depth is of order 10−8.