Temporal Variability of Saturn's H 2 Dayglow and Northern Aurora Observed by Hisaki and Cassini

Clare, L. S. and Badman, S. V. and Kimura, T. and Tsuchiya, F. and Tadokoro, H. and Tao, C. and Kasaba, Y. and Bader, A. and Farr, S. W. and Kinrade, J. and Yoshioka, K. and Yamazaki, A. and Murakami, G. and Yoshikawa, I. and Kita, H. (2026) Temporal Variability of Saturn's H 2 Dayglow and Northern Aurora Observed by Hisaki and Cassini. Journal of Geophysical Research: Space Physics, 131 (6): e2026JA035. ISSN 2169-9402

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Abstract

Plain Language Summary: Saturn's hydrogen atmosphere emits ultraviolet (UV) light from aurorae over the poles and dayglow from the dayside atmosphere. The dayglow is generated by the interaction of solar UV photons with the atmospheric hydrogen and is less explored than the aurorae at Saturn. Investigation of this emission will provide further understanding on the interaction between the activity from the Sun and the planet's atmosphere. Additionally, how the dayglow varies over time and how much the aurorae contribute to the overall emission is not well known. To address these questions, data from two missions, Cassini and Hisaki, are used to determine the total emitted power (both the dayglow and the northern aurora), and its variation over time. The total emitted power reveals significant variation over an approximately 3‐week interval in 2014. The Cassini data allow the contribution from the northern aurora to be determined, which can be as much as 26%. Therefore, the total power is dominated by the dayglow contribution. Finally, the variation of the power is compared to the solar activity and it is concluded that the dayglow is controlled by this activity.