A Rotating Azimuthally Distributed Auroral Current System on Saturn Revealed by the Cassini Spacecraft

Guo, R. L. and Yao, Z. H. and Dunn, W.R. and Palmaerts, B. and Sergis, N. and Grodent, D. C. and Badman, Sarah and Ye, S.-Y. and Pu, Zu-Yin and Mitchell, D. G. and Zhang, B. Z. and Achilleos, N and Coates, A.J. and Wei, Y. and Waite, J.H. and Krupp, N. and Dougherty, M.K. (2021) A Rotating Azimuthally Distributed Auroral Current System on Saturn Revealed by the Cassini Spacecraft. Astrophysical Journal Letters, 919 (2): L25. ISSN 2041-8205

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Abstract

Stunning aurorae are mainly produced when accelerated electrons travel along magnetic field lines to collide with the atmosphere. The motion of electrons often corresponds to the evolution of a magnetic field-aligned current system. In the terrestrial magnetosphere, the current system is formed at the night-side sector, and thus produces an auroral bulge at night. Due to the different energy sources between Saturn and the Earth, it is expected that their auroral current systems are fundamentally different, although the specific auroral driver at Saturn is poorly understood. Using simultaneous measurements of the aurora, particles, magnetic fields, and energetic neutral atoms, we reveal that a chain of paired currents, each of which includes a downward and an upward current branch, is formed in Saturn's magnetosphere, which generates separated auroral patches. These findings inform similar auroral current structures between the Earth and Saturn, while the difference is that Saturn's unique mass and energy sources lead to a rotational characteristic.