A wiggle around a giant: exploring the hot electrons within the Io torus

Abstract

Jupiter exhibits a fundamental rotational periodicity known as System IV that has no widely-accepted explanation, yet is easily observed in ultraviolet emission from the plasma torus generated by the innermost Galilean moon Io. This periodicity around Jupiter maps to a persistent, radially independent subcorotation within the Io plasma torus. In this thesis, we explore the origin and consequences of this periodicity. Using an equatorial chemistry and diffusive transport model, we demonstrate that a prescribed hot electron population produces a coherent wave of heightened energy flow that induces a consistent subcorotation. This additional hot electron population is consistent with the energization produced at high latitude by parallel electric fields induced by Alfvén waves propagating to the planet. The radial independence of this period means that while the generating mechanisms are likely in close proximity to the Io flux tube, the periodicity has dramatic consequences for plasma out at Europa, the next moon outwards and a subject of intense scientific curiosity.