RADIO-EMISSION FROM JUPITER OBSERVED BY ULYSSES BEFORE AND AFTER ENCOUNTER

The polarization and the occurrence probability of the radio emission from Jupiter at 940 and 52 kHz are compared before and after encounter. It is found that, after encounter, the right-hand polarized Main Component of the broad-band kilometric emission (bKOM) is not present while the left-hand polarized Intermittent Component is considerably enhanced. Both the left- and the right-hand components of the hectometric emission (HOM) are essentially absent after encounter. These results, which are almost certainly effects of beaming, are compared with current theoretical ideas. While the 940 kHz observations can be reco nciled fairly easily with HOM theory, the 52 kHz observations raise difficulties for the bKOM.