Heliophysics at the Solar System's most powerful particle accelerator: the COMPASS mission to Jupiter

Jupiter's magnetosphere is an environment of extremes: it has the strongest magnetic field, the fastest spin, and the most active moons that provide plasma to the magnetosphere. While electron energies at the Earth approach 10MeV only during extreme events, electron acceleration to many tens of MeV occurs at Jupiter all the time. Even heavy ions such as oxygen and sulfur are trapped up to hundreds of GeV. The heavy ions released from the moons provide ample opportunity to study mass and charge dependent acceleration processes. While the waves driving acceleration processes at the Earth are found throughout the L-shells of the radiation belts, they are at Jupiter limited to a narrow range, making it easier to disentangle local from non-local acceleration. While dynamics at the Earth is in parts driven by magnetopause shadowing and substorms, Jupiter's belts are embedded so deep within the magnetosphere, that these effects are at least thought to be negligible. Jupiter is therefore in many ways a very well controlled laboratory to study space physics processes that occur also at the Earth and in the rest of the universe. In addition, Jupiter's high energy particles can be explored both in-situ and remotely for example via their X-Ray emissions, providing a stepping stone to extrasolar systems, such as pulsar nebulae or magnetized stars.

Here we will present the results of a concept study for the Comprehensive Observations of Magnetospheric Particle Acceleration, Sources, and Sinks (COMPASS) mission. Despite the general interest in Jupiter's radiation and several missions, no spacecraft spent a lot of time in Jupiter's radiation belts, or even carried instrumentation able to properly perform in this environment and resolve particles at extreme energies. COMPASS will fill this void. It is a spin-stabilized, solar powered spacecraft. A Falcon Heavy Expendable allows it to carry its comprehensive instrument suite and heavy radiation shielding. Its unprecedented capabilities at Jupiter will include energy-resolved measurements of up to 70MeV electrons and 1GeV ions, direct measurements of ion charge states, 3D wave vectors, and global imaging of the electron belts through inverse Compton scattered x-rays.

This presentation will discuss the science opportunities at Jupiter and provide details of the mission design.