Rotating features in Saturn’s magnetosphere revealed by auroral images
J. Kinrade
Lancaster University
S. V. Badman1, K. H. Baines2, B. Bonford3, E. J. Bunce4, J. T. Clarke5, F. Crary6, D. Grodent3, T. Kimura7, H. Melin4, D. G. Mitchell8, J. D. Nichols4, G. Provan4, W. R. Pryor9, A. Radioti3, C. Tao10
Auroral emissions on Earth are driven by interactions between the magnetosphere and the solar wind, whereas further out in the solar system at Saturn the auroral morphology is significantly affected by processes related to the planet’s rapid (~11 h) rotation. Saturn’s auroral ovals are generally brighter at dawn than at dusk, indicating a local time influence by the Sun or solar wind, but the emission intensity also demonstrates a periodic modulation independently in the northern and southern hemispheres, at periods close to that of planetary rotation. These independently rotating intensifications reveal the magnetic field-aligned currents connecting the northern and southern ionospheres to the equatorial magnetosphere and possibly to each other. In addition, auroral enhancements have been associated with the motion of blobs of energetic particles through Saturn’s equatorial magnetosphere, which occurs at a fraction of the planetary rotation rate. Using images of Saturn’s northern UV aurorae taken by the Hubble Space Telescope we will show examples of these types of features, their rotation rates, and describe their relationship to other rotating magnetospheric phenomena. The upcoming Cassini Grand Finale mission in 2016/17 will see the spacecraft make high resolution auroral observations from low altitudes, which together with in-situ field measurements across current system boundaries should further our understanding of Saturn’s aurorae.