A research team from the Planetary Physics and Magnetohydrodynamics Group, in collaboration with scientists from the Earth's Rotation Variation Group at the Shanghai Astronomical Observatory, Chinese Academy of Sciences, has achieved a significant breakthrough in the study of atmospheric dynamics on gaseous giants. For the first time, they have proposed a new mechanism driving prograde equatorial jets (where wind direction aligns with the planet's rotation). This mechanism transcends the limitations of traditional theories regarding atmospheric dynamic processes, revealing the direct regulatory role of deep interior magnetohydrodynamic waves on atmospheric circulation. It offers a fresh perspective for understanding the atmospheric dynamics of gaseous giants. The findings were published online on March 27, 2026, in The Astrophysical Journal Letters, a leading journal in the field of astronomy.

The long-standing mystery of why equatorial jets on gaseous giants like Jupiter and Saturn maintain a prograde direction has been a persistent challenge in planetary science. The origin of these powerful equatorial jets in the atmospheres of these "Jupiter-like" planets has puzzled the planetary physics community for decades¹²³⁴. Theoretically, such jets require a continuous supply of momentum transported to the equator⁵. Building upon an analytical model for equatorial Magneto-Archimedes-Coriolis (eMAC) waves published in 2023 in the Journal of Geophysical Research: Solid Earth (JGR: Solid Earth)⁶, we have, for the first time, applied this analytical solution for magnetohydrodynamic waves to the study of the deep interiors of gaseous giant. This yielded theoretical results that are in excellent agreement with actual observations (see figure below). The results suggest that the mechanism behind the "low-latitude wind fields and jets" observed on Jupiter and Saturn is likely a manifestation of magnetohydrodynamic wave signals generated within the planet's internal stable stratified layer—specifically, the hydrogen-helium immiscible layer, or "helium rain" layer. Confined to the equatorial region, these waves possess low phase velocities, and their perturbations can propagate upward to the weather layer, creating a specific thermal structure that efficiently transports momentum toward the equator.

Figure. Schematic of the analytical eMAC wave model explaining the origin of Jupiter's low-latitude wind field. The center panel shows Jupiter's actual atmospheric circulation wind field; the left panel depicts a scenario without considering internal eMAC waves; the right panel shows the scenario incorporating internal eMAC waves.

This mechanism is closely linked to the evolutionary process of gas giants. As the planet's interior gradually cools, hydrogen and helium separate within a certain pressure range, with helium precipitating out to form "helium rain" ⁷. This process establishes a stable stratified region maintained by a compositional gradient, sandwiched between two convective layers ⁸. The research team confirmed for the first time that this stable layer is the crucial site for the generation of equatorial eMAC waves. To further validate this mechanism, the team employed the internationally utilized MITgcm atmospheric model to conduct high-precision atmospheric dynamics simulations of equatorial wave disturbances. The results indicate that the azimuthal inhomogeneity in the equatorial region induced by these waves can excite Matsuno-Gill modes in the atmosphere ^{9 10}. These modes can efficiently transport angular momentum from off-equatorial regions toward the equator, ultimately leading to the formation of a stable prograde equatorial jet.

This achievement not only provides a novel theoretical explanation for the origin of equatorial jets on gaseous giants but also offers crucial clues for understanding the significant differences in circulation patterns between gaseous giants and ice giants. The scientific significance of this work also lies in its revelation of a universal physical mechanism—the common mechanism by which magnetohydrodynamic waves within stratified bodies drive low-latitude jets—providing a new paradigm for understanding gaseous giant atmospheric dynamics. It is expected to offer crucial theoretical support for interpreting data from future exploration missions to Jupiter, Saturn, and other giant planets.

This work was supported by the National Key Research and Development Program of China (Grant No. 2025YFF0512400), the National Natural Science Foundation of China (Grant Nos. 12425306, 42405129), and other funding sources.

Article Link: https://iopscience.iop.org/article/10.3847/2041-8213/ae518c.

Scientific Contacts:
Lian Yuchen – lianyuchen@shao.ac.cn
Duan Pengshuo – duanps@shao.ac.cn
Kong Dali – dkong@shao.ac.cn

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