Dawn-dusk Asymmetrical Distribution of Saturn’s Cusp

Xu, Yan and Yao, Zhonghua and Arridge, Chris and Zhang, Binzheng and Chen, J.J. and Badman, Sarah and Ray, Licia C and Coates, A.J. and Ye, Sheng-Yi and Qin, Tianshu and Zheng, Z.Q. and Dunn, William R. and Wei, Y. (2026) Dawn-dusk Asymmetrical Distribution of Saturn’s Cusp. Nature Communications. ISSN 2041-1723 (In Press)

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Abstract

Saturn’s magnetosphere, shaped by solar wind interaction with its dipole field, differs from Earth’s due to faster rotation and Enceladus’s internal plasma sources. An ongoing focus of investigation is how the internal plasma sources and rapid rotation result in a different global magnetospheric picture. The magnetospheric cusp, a crucial interaction region between solar wind and planetary magnetic field, serves as an indicator of global magnetic configuration. Here we utilize Cassini observations from2004 to 2010 to study dawn-dusk asymmetry in Saturn’s cusp distribution and extend the number of cusp events from about 11 reported in previous studies to 67. We find peak occurrence in the post-noon sector and signatures extending to post-dusk (near 20 local time), resembling recent observations of Jupiter’s post-dusk cusp. We further examine magnetic topology using high-resolution magnetohydrodynamic simulations to visualize the cusp asymmetry. This is consistent with previous studies but our simulations provide a more detailed view of Saturn’s magnetic topology near the magnetopause. This asymmetry of cusp distribution demonstrates how rapid rotation and internal plasma sources fundamentally alter magnetospheric configuration, offering insights for understanding other rotating planetary systems within and beyond the solar system.