Mechanisms of Saturn's Near-Noon Transient Aurora : In Situ Evidence From Cassini Measurements

Yao, Z. H. and Radioti, A. and Rae, I. J. and Liu, J. and Grodent, D. and Ray, L. C. and Badman, S. V. and Coates, A. J. and Gérard, J. C. and Waite, J. H. and Yates, J. N. and Shi, Q. Q. and Wei, Y. and Bonfond, B. and Dougherty, M. K. and Roussos, E. and Sergis, N. and Palmaerts, B. (2017) Mechanisms of Saturn's Near-Noon Transient Aurora : In Situ Evidence From Cassini Measurements. Geophysical Research Letters, 44 (22). 11,217-11,228. ISSN 0094-8276

Abstract

Although auroral emissions at giant planets have been observed for decades, the physical mechanisms of aurorae at giant planets remain unclear. One key reason is the lack of simultaneous measurements in the magnetosphere while remote sensing of the aurora. We report a dynamic auroral event identified with the Cassini Ultraviolet Imaging Spectrograph (UVIS) at Saturn on 13 July 2008 with coordinated measurements of the magnetic field and plasma in the magnetosphere. The auroral intensification was transient, only lasting for ∼30 min. The magnetic field and plasma are perturbed during the auroral intensification period. We suggest that this intensification was caused by wave mode conversion generated field-aligned currents, and we propose two potential mechanisms for the generation of this plasma wave and the transient auroral intensification. A survey of the Cassini UVIS database reveals that this type of transient auroral intensification is very common (10/11 time sequences, and ∼10% of the total images).