Properties of Saturn's ULF Wave Foreshock: Observations by Cassini

ANDRES, N.; GOMEZ, D. O.; BERTUCCI, C.; MAZELLE, C. X.; DOUGHERTY, M. K.

Congreso; AGU Fall Meeting 2013; 2013

In this work, we present the properties of the waves observed in Saturn's ULF wave foreshock and identify its outer boundary using Cassini Vector Helium Magnetometer (VHM) measurements obtained from Saturn Orbit Insertion (SOI) in June 2004 through August 2005. The amplitude of these waves is usually comparable to the mean magnetic field intensity, while their frequencies in the spacecraft frame yields two clearly differentiated types: one with frequencies below the local proton cyclotron frequency (OmegaH+) and another with frequencies above OmegaH+ . All wave events described are clearly associated to Saturn's foreshock. In particular, the occurrence of ULF foreshock waves is restricted to a region defined by bow shock normal angles smaller than ? 45 degrees. We discuss these results in the light of previous studies on possible wave generation mechanism and compare the ULF wave foreshock boundary geometry with its Terrestrial counterpart.