February 2, 2010
Analysis of periodicities in Saturn kilometric radiation reveals two periods as indicated in this display. The kilometric radio emissions coming from the Northern hemisphere have a period near 10.6 hours, implying a rotation rate in this hemisphere of about 816 degrees per 24 hours. Radio emissions coming from the Southern hemisphere have a period of about 10.8 hours, implying a rotation rate of about 800 degrees per day. Both periods vary with time and the strength of the modulation also varies for both. The dashed line is an estimate of Saturn's internal rotation period (or rotation rate) based on gravity measurements and Saturn's shape. The fact that both radio periods are longer than the internal period is evidence that Saturn's magnetosphere is slipping with respect to the interior of the planet.