Prediction of the Ulysses Jovian hectometric observations

Abstract

The Ulysses unified radio and plasma wave (URAP) experiment is well suited to observe the Jovian hectometric radio emission (HOM) and so complement the observations made by the low‐frequency band receiver on Voyager. When the spacecraft encounters Jupiter, in February 1992, observations will be possible from considerably higher magnetic latitudes, in both hemispheres, than those accessible to Voyager. It should also be possible to determine the source location, as URAP can measure the direction of the incoming waves and all four Stokes parameters. Based upon the HOM beaming and source model of Ladreiter and Leblanc (1990a,b), the following predictions can be made: (1) During the inbound trajectory, Ulysses will, at first, be close to the Jovian equatorial plane when equal amounts of right‐handed (RH) and left‐handed (LH) circularly polarized HOM should be observed from the northern hemisphere and the southern hemisphere, respectively. During the three days immediately before closest approach, the spacecraft will move to a higher northerly magnetic latitude where it will be outside the main HOM emission beam so that a relatively weak RH polarized signal should be observed. (2) At closest approach, Ulysses will be very close to the low‐frequency HOM sources and will cross the HOM shadow zone, which extends out to about 20 Jovian radii (RJ) close to the magnetic equatorial plane. (3) During the outbound trajectory, the spacecraft will be at a fairly high southerly magnetic latitude and outside the main HOM emission beam, so that a relatively weak LH polarized signal should be observed.