Evidence of Enceladus and Tethys microsignatures

Abstract

We present evidence of two icy satellite microsignatures in the Cassini LEMMS data. Just upstream of Enceladus, a deep and narrow decrease in the flux of several MeV electrons is consistent with a recent absorption by that moon. This microsignature is collocated with a deep depletion in the MeV proton flux. The proton feature is much wider than the satellite diameter, suggesting multiple interactions and/or losses to the E Ring and neutral gas. An observed increase in proton flux toward the planet suggests a possible inner magnetospheric source. A decrease in the low energy electron intensity downstream of Tethys is also consistent with a microsignature approximately the size of the satellite that has drifted slightly toward the planet near midnight. Modeling suggests that microsignatures near Tethys' orbit would persist for more than a complete rotation of Saturn and the radial diffusion coefficient is about 10^-9 R_S²/s.