Jupiter's bright persistent polar aurora and Earth's dark polar region
indicate that the planets' magnetospheric topologies are very different.
High-resolution global simulations show that the reconnection rate at the
interface between the interplanetary and jovian magnetic fields is too slow to
generate a magnetically open, Earth-like polar cap on the timescale of
planetary rotation, resulting in only a small crescent-shaped region of
magnetic flux interconnected with the interplanetary magnetic field. Most of
the jovian polar cap is threaded by helical magnetic flux that closes within
the planetary interior, extends into the outer magnetosphere and piles-up near
its dawnside flank where fast differential plasma rotation pulls the field
lines sunward. This unusual magnetic topology provides new insights into
Jupiter's distinctive auroral morphology
