ORDINARY AND Z-MODE EMISSIONS FROM THE JOVIAN POLAR-REGION

The Ulysses Unified Radio and Plasma (URAP) experiment has detected a new component of Jupiter's radio spectrum in the frequency range from about 10 to 30 kHz. This component is emitted in the magnetoionic ordi nary mode from a localized corotating source in the northern polar reg ion. The source is centered at system III longitude 208-degrees, near the meridian containing the North magnetic dipole axis, at a distance of nearly 4R(J) from the planet and near the last closed field line. T he emission frequency is somewhat above the electron plasma frequency in the source region, but well below the electron gyrofrequency. Accom panying this 0-mode emission at lower frequencies is intense Z-mode em ission, which is likely to play a significant role in the generation o f the 0-mode.