Interhemispheric asymmetries in Saturn’s UV aurora
Magnetospheres
Sarah
Badman
Date Submitted
2019-03-15 15:14:39
Lancaster University
S.V. Badman (Lancaster Uni.), L. Lamy (Obs. de Paris), W. Pryor (Central Arizona College), E. J. Bunce (Uni. of Leicester), R. Prange (Obs. de Paris), P. Zarka (Obs. de Paris), B. Cecconi (Obs. de Paris), J. D. Nichols (Uni. of Leicester), J. T. Clarke (Boston Uni.), G. J. Hunt (Imperial College London), A. Radioti (Uni. de Liege), J. Kinrade (Lancaster Uni.), A. Bader (Lancaster Uni.), W. S. Kurth (Uni. of Iowa), D. G. Mitchell (JHU/APL), M. K. Dougherty (Imperial College London)
Simultaneous observations of Saturn's northern and southern UV aurora were acquired on 19 August 2016 by the Hubble Space Telescope and Cassini mission, respectively. Some auroral features were present in both hemispheres, including a dawn arc and a patch of lower latitude emission near noon. However, while the dawnside and noon sectors were brighter in the north, the southern aurorae were dominated by a bright, high latitude arc moving from the dusk to midnight sectors. Large-scale asymmetries can be attributed to the higher magnetic field strength and enhanced solar-driven conductivity in the north, plus modulation of intensities in both hemispheres by rotating field-aligned currents. Measurements made in situ by Cassini in the southern hemisphere indicate that the bright, high latitude dusk arc occurred adjacent to the open field region. This arc persisted for >8 h and rotated at ~70% corotation to the nightside. No counterpart was observed in the north although transient (10 min) flashes were observed at other times in this sector. The higher latitude, apparently persistent, rotating arc seen in the south is likely driven by a different process than the lower latitude, transient, non-rotating flashes captured in the north.
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