Seasonal variation of north–south asymmetry in the intensity of Saturn Kilometric Radiation from 2004 to 2017

Yuki Nakamura, Yasumasa Kasaba, Tomoki Kimura, Laurent Lamy, Baptiste Cecconi, Georg Fischer, Ayumu Sasaki, Chihiro Tao, Fuminori Tsuchiya, Hiroaki Misawa, Atsushi Kumamoto, Akira Morioka

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

This study investigates the long-term variation of Saturn Kilometric Radiation (SKR) intensity observed by the Radio and Plasma Wave Science (RPWS) instrument on board the Cassini spacecraft from 2004 (southern summer) to 2017 (northern summer). The results show that the SKR intensity was brighter in the summer hemisphere than in the winter hemisphere, which was clearly seen in the south-to-north SKR intensity ratio. Over the long-term, the southern SKR intensity became 100 times smaller during northern summer, while the northern SKR intensity remained fairly constant. It means that the reversal in the intensity ratio was mainly caused by the long-term reduction of southern SKR intensity as Saturn's southern hemisphere moved from summer to winter, not the enhancement of northern SKR from winter to summer. We also investigated the possible contributions from the long-term solar EUV flux and solar wind dynamic pressure during the solar cycles 23 and 24, but we found that their impact on the SKR long-term variations was less than Saturn's seasonal changes associated with the variation of the tilt of its rotational axis with respect to the Sun. We further compared the long-term variation of the SKR intensity and the SKR period over half a Kronian year. The former showed more systematic variations which do not compare to those seen in the SKR periods.

Original languageEnglish
Article number104711
JournalPlanetary and Space Science
Volume178
DOIs
Publication statusPublished - 2019 Nov 15

Keywords

  • Aurora
  • Saturn
  • Saturn Kilometric Radiation (SKR)
  • Seasonal variation

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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