Energetic neutral atom imaging reveals nearly 11-year cycle of the ring current of Saturn

Abstract The drift motion of energetic charged particles can generate an azimuthal electric current around the planet known as the ring current, which regulates the field configuration of the magnetosphere. However, limited coverage of in-situ measurements makes it challenging to investigate the long-term variations of the global ring current. Taking advantage of the energetic neutral atom (ENA) imaging onboard the Cassini mission, we present a nearly 11-year cycle of the suprathermal ring current populations in Saturn’s magnetosphere. We find that the peak location of the suprathermal ring current in local time oscillates between post-midnight and pre-midnight sectors, and its intensity minimizes during the solar maximum. These results indicate that the modulation of the suprathermal ring current is closely related to the solar cycle. Our analysis also offers a preview of the ring current at other giant planets, such as Jupiter, which will be imaged by ENA cameras onboard the JUICE mission.