ORIGIN OF THE O-UP IONS IN THE HELIOSPHERE( PICK)

The main sources for the ions in the interplanetary medium are the sol ar wind and the interstellar gas intruding into the heliosphere. Other sources, i.e. comets and planets can, however, contribute significant ly locally. We present approximate expressions for deriving fluxes of pick-up ions originating from local neutral gas sources. Since the Io- torus is thought to be a relatively strong emitter of fast atoms, part icular O and S, we used the O+ data obtained by SWICS-Ulysses as a fun ction of distance from Jupiter, both in and out-off the ecliptic plane in order to recognize a possible contribution of the Ionian source to the measured O+. We find that - except for a very limited zone near t he Jovian magnetosphere - the contribution of the Io-torus to the Of f luxes is minor, thus confirming our previous results on the pick-up H, He+, N+, O+, and Ne+ fluxes of interstellar origin.