Update on Saturn’s energetic electron periodicities

摘要

The periodicities in fluxes of energetic electrons (110–365 keV) in Saturn’s magnetosphere were determined from late 2004 to mid-2016. The electron periods were calculated using Lomb periodogram analyses within windows of 200 days at sliding intervals of 10 days, which tracked changes in the periodicity. Sometimes the periodicity showed a clear duality, as in 2007–2008, while at other times the two periods came together so closely as to be indistinguishable, as after equinox in 2010 and in 2015. At still other times, the periodicity apparently vanished altogether, as in 2014. These periodicities generally agreed with those of other phenomena such as the magnetic field and radio emissions. Whether dual or mono, the periods generally remained between 10.58 h and 10.84 h, with two statistical peaks at ~10.68 h and ~10.81 h. This observation suggests that magnetospheric periodicities at Saturn lie within a limited range of values, which places constraints on the generative mechanism for the phenomena.