Neptune radio emission: Predictions based on planetary scaling laws

Abstract

In this paper a prediction is advanced concerning Neptune's low‐frequency radio emission based on the radiometric Bode's law for radio planets in combination with the magnetostrophic scaling law for magnetized planets. We expect the total emitted radio power to be about 1.6 × 107 W, very nearly the same as that predicted and observed for Uranus. Possible emission spectral shapes, based on Saturn and earth‐like models, are shown. Using these models, the radio emission frequency range is predicted to extend from approximately 100 to just over 1000 kHz, with a spectral peak between 350 and 500 kHz. If radiation is beamed approximately in the sunward direction, Neptune should be detectable by the planetary radio astronomy experiment onboard the Voyager spacecraft sometime between 45 and 90 days before closest approach. This detection is likely to represent the first direct evidence of a Neptune magnetic field. Possible implications for Neptune's magnetosphere with regard to the time of first detection are discussed.