The Composition of Very Energetic Heavy Ions in Jupiter’s Magnetosphere

Jupiter hosts the most energetic, intense and ion-rich radiation belts in the solar system. Understanding the composition and distribution of their heavy ions is essential for constraining source, acceleration, and loss processes across an ion mass and energy range not typically accessible in other planetary magnetospheres. Energetic heavy ions may alter Jovian moon surfaces and rings, generate X-ray emissions in the Jovian system, and pose risks to spacecraft via single event effects. Despite their importance, relatively little is known about their global distribution and dynamics within the Jovian magnetosphere, particularly above several MeV nucleon–1 or for species different than sulfur or oxygen. Here we survey the full Heavy Ion Counter dataset from the Galileo mission to characterize the composition of Jupiter’s >5 MeV nucleon−1 ions (Z > 6), with an extra focus on lesser-studied species. We unambiguously resolve 10 different ion species and provide estimates of their energy and distance dependent relative abundances. Several new species are resolved (N, Ne, Si, K, and/or Ca and possibly Fe), each likely associated with different magnetospheric, weathering, and/or heliospheric processes. A key finding is that abundances of species like carbon, neon and silicon are reminiscent of those in solar energetic particles and comparable to or larger than magnetospheric sulfur, indicating a considerable solar input into Jupiter’s heavy ion radiation belts. A considerable abundance enhancement of N between Io and Ganymede, hints that a N source may exist in Jupiter’s magnetosphere.