Fig. 1. Sketch of the field and energetic particle structure corresponding to the duskside outbound Ulysses pass, where the background dot density gives a qualitative indication of the flux levels of 1 MeV ions. Two large scale ion regions are evident within the Jovian magnetosphere: the magnetodisk plasma sheet and the high latitude outer magnetosphere layer (adapted from Cowley et al., 1996).

Fig. 2. (a) HISCALE energetic ion and electron intensities (top panel), spectral indexes for energetic ions and electrons (second and third panels), ion abundance ratio (fourth panel), magnetic field strength (fifth panel) and the magnetic dipole latitude θ (bottom panel) as a function of time, during the inbound Ulysses pass of Jovian magnetosphere. The normal dashed lines show the bow shock (BS) and the magnetopause (MP) crossings, and the principal energetic particle flux enhancements (P), observed near minima in the magnetic field strength and the magnetic latitude (magnetodisk plasma sheet approaches). (b) Observations for the outbound pass in the same format as Fig. 2a.

Fig. 3. (From top to bottom) Ion fluxes from three different energy channels (P′1, P′4 and P′8), spectral indexes for ions (P′4/P′8) and electrons (DE1/DE4), fluxes of low energy electrons (DE1), middle energy protons (W1) and high energy heavy ions (Z3), and three component of the magnetic field for a representative energetic particle event observed near the magnetodisk current sheet (event H of Fig. 2b). Notice the almost simultaneous (within a few minutes) flux variations of different particle (ion) species (energies).

Fig. 4. (a) Observations in the same format as Fig. 2a but on an expanded time basis. The normal solid lines show spectral index peaks and minor energetic particle flux enhancements (HL) observed at higher magnetic latitude far from the magnetodisk plasma sheet inbound. (b) Observations in the same format as Fig. 4a, but on an expanded time basis. The normal solid lines have been drawn around principal electron spectral index peaks at high latitudes (HL).

Fig. 5. (a) Observations for a representative energetic particle event in the high latitude outer magnetosphere (on Ulysses outbound pass), in the same format as Fig. 3. Notice the dispersion in the fluxes of various particle (ion) species (energies). (b) As in Fig. 5a.

Fig. 6. (From top to bottom) Spectral index (DE1/DE4) and fluxes of energetic electrons (DE1), and the dipole latitude θ of Ulysses spacecraft on its outbound pass through the dusk outer magnetosphere, as a function of time. Maxima of the spectral index and minima in electron fluxes were observed at times of (or in phase with) boundary layer crossings. Evident is a 10 h periodic variation of the electron spectral index. The observations are consistent with energetic electron layers near the magnetopause, which move periodically inward–outward at almost the Jupiter rotation period (10 h). The small arrows indicate 40 min bursts superimposed on the general profile.

Fig. 7. High time resolution energetic proton and electron fluxes and spectral indexes on d 43, 1992 (near the high latitude magnetopause). Evident are 40 min periodicities.

Fig. 8. Representative pitch angle distributions of normalized high energy (>2.5 MeV) heavy (Z>5) ion intensities during the onset and the decay phases of the high latitude events shown in Fig. 5 (at times indicated by arrows in Fig. 5a and b). The change of the sectors (4–8/7) detecting high/low particle intensities at 90° pitch angles suggests the existence of intensity gradients in opposite directions during the onset and the decay of events (see the description in the text). The observations suggest the existence of energetic particle layers in the high latitude outer magnetosphere.

Fig. 9. Auto-correlation analysis results on the electron spectral ratio DE1/DE4 for the time period 0200 UT / d 42–1200 UT / d 43 illustrating a significant periodicity at 10 h.

Fig. 10. Lines produced by the least square method for the times of occurrence of spectral maxima at high latitudes, during the inbound and the outbound Ulysses pass of the Jovian magnetosphere, for ions (a) and electrons (b). The observations suggest a significant a 3 h (or 7 h) phase shift between the inbound and outbound observations at high latitudes.

Fig. 11. Schematic indicating a model with the inner, the middle and the outer Jovian magnetosphere, adapted from Smith et al. (1976), where we have added dots indicating a particle population originating from the poles of Jupiter and propagating in the high latitude magnetosphere. The periodic approach of a spacecraft (due to the planet's rotation) to the two major particle regions, the magnetodisk plasma sheet and the high latitude outer magnetosphere layer, produces 10 or 5 h periodicities (dependent on the relative position of the spacecraft) and two different kinds of effects in particle data.