Quasi‐periodic behavior of ion events and wave activity upstream from Jupiter's Bow Shock: Ulysses' observations

A new insight into the ways that the Jovian magnetosphere influences the near Jupiter interplanetary space becomes possible thanks to Ulysses' collection of magnetic field, plasma and energetic ion (HI‐SCALE) data during its inbound trajectory (d22–d34, 1992). The most striking new results from the analysis of those data are the following: a) presence of large amplitude (ΔB ⟂ /B≈1) near plane polarized Alfvén waves upstream from the Jovian bow shock with a period equal to the planet's rotation (∼10h) at times when the Interplanetary Magnetic Field (IMF) was in contact with the bow shock/magnetopause and lay well outside the ecliptic; b) observation of ∼10h quasi‐periodic variation in the ion plasma and energetic ion data up to energies of ∼2 MeV, c) existence of a variation with a period 2.5 h ≤T ≤6.5 h in the magnetic field and the ion data, in several cases, d) detection of magnetic waves and charged particle modulation with a period of ∼40min, e) observation of an ∼10 h inward/outward motion of the Jovian magnetopause. The observations are consistent with generation of the low frequency upstream (Alfvén) waves through periodic injection of plasma/energetic ions from within the magnetosphere into the upstream region.