Solar wind periodicity in energetic electrons at Saturn

Abstract

[1] 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 RS 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.