  Ulysses investigated the high latitude Jovian magnetosphere for a second time
after Pioneer 11 mission and gave us the opportunity to search the structure
and the dynamics of this giant magnetosphere above the magnetodisc.
Kivelson(1976) and Kennel & Coroniti(1979) reported that Pioneer 11 observed
energetic particle intensities at high latitudes at the same level with those
measured in the plasma sheet and inferred that they were not consistent with
the magnetodisc model. Ulysses observations supported the idea about a
large-scale layer of energetic ions and electrons in the outer high latitude
Jovian magnetosphere (Cowley et al.1996; Anagnostopoulos et al. 2001). This
study perform a number of further tests for the existence of the large scale
layer of energetic ions in the outer high latitude Jovian magnetosphere by
studying appropriate cross-B field anisotropies in order to monitor the ion
northward/southward intensity gradients. In particular, we examined
Ulysses/HI-SCALE observations of energetic ions with large gyro-radius
(0.5-1.6MeV protons and >2.5MeV heavy(Z>5) ions) in order to compare instant
intensity changes with remote sensing intensity gradients. Our analysis
confirms the existence of an energetic particle layer in the north hemisphere,
during the inbound trajectory of Ulysses traveling at moderate latitudes, and
in the south high-latitude duskside magnetosphere, during the outbound segment
of the spacecraft trajectory. Our Ulysses/HI-SCALE data analysis also provides
evidence for the detection of an energetic proton magnetopause boundary layer
during the outbound trajectory of the spacecraft. During Ulysses flyby of
Jupiter the almost permanent appearance of alternative northward and southward
intensity gradients suggests that the high latitude layer appeared to be a
third major area of energetic particles, which coexisted with the radiation
belts and the magnetodisc.
