Kinematics of Saturn's spokes

Voyager 2 images of Saturn's rings have been analyzed for spoke activity. More than 80 and 40 different spokes have been measured at the morning and at the evening ansa, respectively. Higher rate of spoke formation has been found at 145 + or 15 deg SLS and at 305 + or - 15 deg SLS which persisted for at least 3 Saturn revolutions. Higher spoke activity (formation and growth in width) by more than a factor 3 has been observed over the nightside hemisphere of Saturn than over the dayside hemisphere. The age distribution (i.e., time from radial formation until observation, assuming Keplerian shear) of the leading (old) edges of spokes has its maximum at approximately 9,000 s and 6,000 s for spokes observed at the morning ansa and at the evening ansa, respectively. The highest spoke age observed is approximately 20,000 s.