Electron Pitch Angle Distributions Along Field Lines Connected to the Auroral Region from ~25 to ~1.2 RJ Measured by the Jovian Auroral Distributions Experiment-Electrons (JADE-E) on Juno

The Jovian Auroral Distributions Experiment (JADE) on Juno provides critical in situ measurements of electrons and ions needed to understand the plasma distributions and processes that fill the Jovian magnetosphere and ultimately produce Jupiter’s bright and dynamic aurora. JADE is an instrument suite that includes two essentially identical electron sensors (JADE-Es) and a single ion sensor (JADE-I). JADE-E measures electron energy distributions from ~0.1 to 100 keV and provides detailed electron pitch angle distributions (PAD) at ~7.5° resolution.

Juno’s trajectories in the northern hemisphere have allowed JADE to sample electron energy and pitch angle distributions on field lines connected to the auroral regions from as close as ~1.2 RJ all the way to distances greater than 25 RJ. Here, we report on the evolution of these distributions. Specifically, the PADs change from mostly uniform at distances greater than ~20 RJ, to butterfly from ~18 to ~12 RJ, to field aligned or pancake, depending on the energy, closer to Jupiter. Below ~1.5 RJ, electron beams and loss cones are observed.