How Jupiter's Unusual Magnetospheric Topology Structures Its Aurora

TL;DR

Jupiter's unique magnetospheric topology, characterized by closed magnetic flux and slow reconnection rates, explains its distinctive auroral features, contrasting with Earth's open polar cap structure.

Contribution

This study reveals that Jupiter's magnetospheric topology differs fundamentally from Earth's, affecting its auroral morphology and magnetic flux distribution.

Findings

Reconnection rate at Jupiter's magnetopause is too slow to open a large polar cap.

Most of Jupiter's polar region is threaded by closed magnetic flux.

Jupiter's magnetic topology leads to a small, crescent-shaped open flux region.

Abstract

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.