Earth-based monitoring of Io torus Proposition for a Community Project

The moon Io, the most active volcanic body in the Solar System,  is the “energy convertor” of the Jupiter system: indeed, Io’s interior is  continuously heated by tidal interactions with Jupiter and the other Galilean moons, while its volcanic activity is the main source of its neutral and plasma torus and generates the Jovian magnetodisk via complex processes likely related to a centrifugal instability.

A number of spacecraft have flown by Jupiter or have been placed into orbit around the planet. Some of them crossed the Io Plasma Torus (IPT), which is the main source of charged particles for the magnetosphere of Jupiter, revealing the complex spatial structure of the IPT. As an important complement, observations of the IPT from the Earth’s surface that are presented at this session, together with observations from Earth orbit (JAXA’s Hisaki) have revealed not only that the spatial structure of the IPT is complex, but also that it displays a large temporal variability over a broad spectrum of timescales, from hours to decades. Achieving a deeper understanding of the sources that drive the complex spatial structure and temporal variability of the IPT remains a very challenging open scientific question. In return, addressing this challenge will provide us with a key piece in the assembly of the puzzle of the Jupiter System.

While a new international flotilla of spacecraft is heading to Jupiter, time is ripe to unite all Io and IPT observers, space-based and Earth-based, to contribute to an around-the-world program of continuous observations. By the addition of observations at different longitudes from America, Hawaii, Japan, China, Europe and Africa, it will be possible to retrieve the complexity of the temporal variability of the IPT, while providing unique support to current Juno observations and upcoming observations by JUICE, Europa Clipper, TianWen-4 and hopefully LAPYUTA.

In this talk, we will review the rich diversity of IPT observations from space and from Earth, propose a modelling tool to assimilate all data into a single model of the Io torus, and propose that the Io and Jupiter science community work together to establish this joint endeavor as a major international scientific program.