Jupiter, the largest planet in the solar system, possesses the largest planetary magnetosphere. Inside the magnetosphere, the planet's fast rotation and volcanic material supplied by the moon Io build a vast, ring-shaped magnetodisk current sheet. For decades, this magnetodisk was pictured as a relatively smooth sheet that rocks up and down as Jupiter's tilted magnetic axis spins around once every ten hours. New observations from NASA's Juno spacecraft show that, during active periods, the magnetodisk is crumpled into a rippling, wave-like structure.
An international team led by researchers at Shandong University analyzed Juno's magnetic field and energetic particle data from multiple events in the Jovian magnetodisk. Normally, the spacecraft should cross the current sheet twice per rotation. Instead, during magnetodisk reconnection events Juno crossed the current sheet again and again — in one case four times within only ten minutes — and nearly every crossing carried the clear magnetic signature of reconnection, together with bursts of energized electrons and ions.
Careful analysis of the orientation of the current sheet showed that it does not simply flap up and down. Instead, it undulates in a kink-like, surface-wave manner, with individual ripples lasting from several minutes to over an hour. The researchers conclude that numerous small reconnection sites, discretely distributed across roughly one hundred degrees of longitude, continually break the disk's magnetic field lines and push the current sheet away from its equilibrium position. Because Jupiter's magnetosphere rotates so quickly, the entire rippled current sheet is carried around with the planet like a crumpled tablecloth spinning on a turntable.
This behavior differs fundamentally from the flapping waves seen in Earth's magnetotail, where a kink wave travels away from a reconnection site. At Jupiter, reconnection signatures appear at almost every crossing and the motion shows no fixed period, which rules out a simple traveling wave and points instead to a rotating, rippled current sheet.
The finding has wide implications. The rippling current sheet may affect how volcanic particles from Io are transported and accelerated to fill the magnetodisk with energetic particles that can be injected toward the inner magnetosphere or channeled into Jupiter's polar auroras, and complicate the magnetic linkage between the planet's ionosphere and its magnetodisk. It shows that the Jovian magnetodisk is a highly structured, dynamic environment rather than a quiet rotating sheet.
The study was published in Science China Earth Sciences. Ruilong Guo of Shandong University is the first and corresponding author of the paper.
This work was supported by the National Natural Science Foundation of China and the Shandong Provincial Natural Science Foundation.
See the article:
Ruilong GUO, Jinyan ZHAO, Yuchen XIAO, Denis GRODENT, Zhonghua YAO, Bertrand BONFOND, Quanqi SHI. 2026. Rippling current sheet generated by magnetodisk reconnection on Jupiter. SCIENCE CHINA Earth Sciences, 69(10), 3619-3625, https://doi.org/10.1007/s11430-025-1870-9
Science China Earth Sciences
Observational study