Magnetic phase structure of Saturn's 10.7 h oscillations

Abstract

AbstractA source of Saturn's magnetic 10.7 h period oscillations has yet to be identified. The oscillations are known to consist of signals with slightly different periods from separate northern and southern sources. Here we present a novel way of examining observations, focusing on signal phase. We show that although the signals are highly periodic they are usually not sinusoidal and that there are differences in both phase structure and polarization between the outer magnetosphere (on the nightside) and the inner dipolar region. Paying particular attention to the deep midtail passes of 2006, the contrasting behavior between the inner and outer regions is clear with approximate sinusoidal behavior in the dipolar region and a pulse‐like signal once per cycle in the tail. The latter structure seems to indicate that tail magnetic stress is released impulsively once per cycle in the tail. After equinox, in 2010–2011, we find a different picture in the premidnight sector. The predetermined northern and southern frequencies are closer together and apparently show sudden shifts. Our signal reconstruction approach finds instances where it is likely that the narrow band filtering is not able to track completely the basic north and south periods as we find phase jumps indicating unpredicted beats.