A Mechanism for Electrostatic Solitary Waves Observed in Ganymede’s Magnetopause

Abstract On 2021 June 7, the Juno spacecraft carried out a close flyby of Ganymede, Jupiter’s largest moon, traversing through the previously unexplored wake region as well as the magnetopause with a closest approach altitude of 1047 km. Electrostatic solitary waves (ESWs) were observed in the magnetopause and the wake region, raising fundamental questions about their origin. We explore the generation mechanism of ESWs at Ganymede’s magnetopause boundary in terms of slow and fast ion-acoustic and electron-acoustic solitons. We model Ganymede’s magnetopause using a fluid-magnetized plasma consisting of warm H + and O + ions, two counterstreaming electron beams, and κ -distributed suprathermal electrons. The model demonstrates that the presence of symmetric electron beams supports the coexistence of slow and fast ion-acoustic solitons, while in the presence of asymmetric electron beams, in addition to slow and fast ion-acoustic solitons, electron-acoustic solitons also exist. The predicted electric field amplitudes ∼(3–527) V m −1 and frequencies (17 Hz–1 kHz) can aptly explain the spacecraft measurements. This provides a explanation of the observed ESWs at the magnetopause. The model also predicts a plausible range of electric field amplitude and frequency, which can form the basis for the future observation by the Jupiter Icy Moons Explorer mission.