Closed Fluxtubes and Dispersive Proton Conics at Jupiter's Polar Cap.

Abstract

Two distinct proton populations are observed over Jupiter's southern polar cap: a ∼1 keV core population and ∼1–300 keV dispersive conic population at 6–7 RJ planetocentric distance. We find the 1 keV core protons are likely the seed population for the higher‐energy dispersive conics, which are accelerated from a distance of ∼3–5 RJ. Transient wave‐particle heating in a “pressure‐cooker” process is likely responsible for this proton acceleration. The plasma characteristics and composition during this period show Jupiter's polar‐most field lines can be topologically closed, with conjugate magnetic footpoints connected to both hemispheres. Finally, these observations demonstrate energetic protons can be accelerated into Jupiter's magnetotail via wave‐particle coupling.