First Observation of Electron Rolling‐Pin Distribution in Jupiter's Magnetosphere

Abstract

The electron rolling‐pin distribution, showing electron pitch angles primarily at 0°, 90°, and 180°, has been widely studied in the Earth's magnetosphere, but has never been reported in other planetary environments. Here, by utilizing the Jupiter Near‐polar Orbiter (Juno) measurements, we report for the first time the electron rolling‐pin distribution in Jupiter's magnetosphere. We reveal the energy range of such distribution and find it appears only above 19.5 keV, falling well into the suprathermal energy range. Moreover, we quantitively reproduce the formation processes of such distribution by using an analytical model. Gratifyingly, the distribution derived from the analytical model agrees well with the Juno observations, indicating such distribution is formed by the combination of global‐scale Fermi acceleration and local‐scale betatron acceleration. These results, demonstrating that the electron rolling‐pin distribution exists beyond the Earth, can improve our knowledge of electron dynamics in planetary magnetosphere.