Unusually short period in electrons at Saturn

Abstract

When subject to Lomb periodogram analyses, fluxes of energetic electrons (27-496keV) observed during the first 245days of 2012 exhibit both mono and dual periods depending on energy. For E < 100keV electrons, dual periods at 9.95hours and 10.64hours are evident, with the strongest signal at the shortest period. For higher energy electrons, only the period at 10.64hours is evident. The 9.95hour period is the shortest period ever measured for Saturn's magnetosphere, and is even shorter than the ∼10.5hour period suggested by studies of Saturn's gravity field and cloud vorticity. If Saturn's magnetospheric periodicities are driven by ionospheric vortices, as suggested by some models, then their speeds would need to be super-rotational to sustain the 9.95hour period reported here. © 2012. American Geophysical Union. All Rights Reserved.