Juno made a close flyby of Ganymede and flew through its magnetosphere on 7 June 2021, including an outbound crossing of Ganymede's upstream magnetopause. We present plasma and magnetic field observations near the upstream magnetopause from Juno's Jovian Auroral Distributions Experiment (JADE) and magnetometer. JADE observed enhanced electron fluxes, including field-aligned electrons accelerated up to 2–3 keV/q, some having bidirectional pitch angle distributions, as Juno crossed Ganymede's magnetopause. Energy enhancements of cold protons and heavy ions originating from Ganymede were also observed on approach to the magnetopause. We interpret the presence of accelerated, field-aligned electrons as indicating that magnetic reconnection is occurring on magnetic field lines that connect the spacecraft to Ganymede's magnetopause at that time. Counter-streaming electrons observed on both sides of the magnetopause suggest the presence of multiple reconnection sites, both north and south of the spacecraft.
All Science Journal Classification (ASJC) codes
- General Earth and Planetary Sciences
- Ganymede's magnetosphere
- Juno flyby
- electron acceleration
- magnetic reconnection