부산대학교 도서관

This study presents evidence of stably trapped electrons at Jupiter's moon Ganymede. We model energetic electron pitch angle distributions and compare them to observations from the Galileo Energetic Particle Detector to identify signatures of trapped particles during the G28 encounter. We trace electron trajectories to show that they enter Ganymede's mini‐magnetospheric environment, become trapped, and drift around the moon for up to 30 min, in some cases stably orbiting the moon multiple times. Conservation of the first adiabatic invariant partially contributes to energy changes throughout the electrons' orbits, with additional acceleration driven by local electric fields, before they return to Jupiter's magnetosphere or impact the surface. These trapped particles manifest as an electron population with an enhanced flux compared to elsewhere within the mini‐magnetosphere that are detectable by future spacecraft. Plain Language Summary: The magnetized planets of the solar system are known to possess a population of high‐energy, orbiting electrons that are sustained for extended timescales. By comparison, Ganymede, the only moon in the solar system confirmed to have its own permanent magnetic field, should also retain a similar population of trapped particles. Observations from the Galileo mission hint at the existence of electrons that may be locally trapped at the moon, but information regarding their origin and the mechanism behind trapping these electrons is unknown. Furthermore, there are no constraints on the processes that help sustain such a trapped population, and the timescales over which they are maintained at Ganymede remain unknown. In this study, we provide evidence that trapped electrons exist at Ganymede, identify the mechanisms driving their dynamics, and answer open questions about the moon's local energetic particle environment. Key Points: We compare Galileo G28 energetic electron data with test particle tracing to identify a population of trapped electrons at GanymedeWe achieve a robust match between the energetic electron pitch angle distributions from our model compared to those observed by GalileoElectrons follow stable orbits that can encircle the moon multiple times before being lost to the surface or to Jupiter's magnetosphere [ABSTRACT FROM AUTHOR]