Solar wind periodicity in energetic electrons at Saturn

Abstract

Fluxes of energetic electrons (110-365 keV) have been subjected to a long-term Lomb periodogram analysis from the middle of 2004 to the middle of 2009. Fluxes within 20 R_S and outside the magnetopause were excluded, so only fluxes within the magnetosphere were included in the analysis. The periodicity “box” was expanded from 5 hours to 50 days. In addition to the familiar rotational period near 10.8 hours, the electron fluxes exhibited a strong periodicity near 26 days (the solar wind period) and also a weaker periodicity near 13 days (half the solar wind period). A simulated periodogram using a “rotating anomaly” as it would be seen from the Cassini orbit does not display 26-day and 13-day periods, so the solar wind periodicity cannot result from a possible orbital resonance. The long-term electron periodogram does not show any periods associated with the periods of Saturn's moons.