Origin of Saturn's aurora:: Simultaneous observations by Cassini and the Hubble Space Telescope - Bunce,EJ; Arridge,CS; Clarke,JT; Coates,AJ; Cowley,SWH; Dougherty,MK; Gerard,J-C; Grodent,D; Hansen,KC; Nichols,JD; Southwood,DJ; Talboys,DL (JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, 2008)