  Even though the solar wind is highly supersonic, intense ultra-low frequency
(ULF) wave activity has been detected in regions just upstream of the bow
shocks of magnetized planets. This feature was first observed ahead of the
Earth's bow shock, and the corresponding region was called the ULF wave
foreshock, which is embedded within the planet's foreshock. The properties as
well as the spatial distribution of ULF waves within the Earth's foreshock have
been extensively studied over the last three decades and have been explained as
a result of plasma instabilities triggered by solar wind ions backstreaming
from the bow shock. Since July 2004, the Cassini spacecraft has characterized
the Saturnian plasma environment including its upstream region. Since Cassini's
Saturn orbit insertion (SOI) in June 2004 through August 2005, we conducted a
detailed survey and analysis of observations made by the Vector Helium
Magnetometer (VHM). The purpose of the present study is to characterize the
properties of waves observed in Saturn's ULF wave foreshock and identify its
boundary using single spacecraft techniques. 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 of
waves: one with frequencies below the local proton cyclotron frequency (\Omega
H+) and another with frequencies above \Omega H+. All the wave crossings
described here, clearly show that these waves are associated to Saturn's
foreshock. In particular, the presence of waves is associated with the change
in \theta Bn to quasi-parallel geometries. Our results show the existence of a
clear boundary for Saturn's ULF wave foreshock, compatible with \theta Bn =
45{\deg} surfaces.
