Solar wind periodicities in thermal electrons at Saturn

Lomb periodogram analyses were applied to all thermal electron data from the Cassini Plasma Science (CAPS) instrument from mid-2004 to mid-2011. Very strong periods at ~26 days were observed in the fluxes of electrons with energies less than 1000 eV. At higher energies, such a strong solar wind period was not apparent, and numerous signals appeared between ~5 d and ~22 d for E > 100 eV. The amplitudes of all these signals greatly exceeded those recognized in the electrons at the ~10.7 h period related to planetary rotation. A simulation using Cassini orbits and a 2D model of electron fluxes indicate that the 5-22 d periods were caused by the spacecraft orbits in to and out of electron radiation belts. Definitive signals do not exist at the periods of Saturn's moons.