  Saturn's magnetospheric magnetic field, planetary radio emissions, plasma
populations and magnetospheric structure are all known to be modulated at
periods close to the assumed rotation period of the planetary interior. These
oscillations are readily apparent despite the high degree of axi-symmetry in
the internally produced magnetic field of the planet, and have different
rotation periods in the northern and southern hemispheres. In this paper we
study the spatial structure of (near-) planetary period magnetic field
oscillations in Saturn's equatorial magnetosphere. Extending previous analyses
of these phenomena, we include all suitable data from the entire Cassini
mission during its orbital tour of the planet, so as to be able to quantify
both the amplitude and phase of these field oscillations throughout Saturn's
equatorial plane, to distances of 30 planetary radii. We study the structure of
these field oscillations in view of both independently rotating northern and
southern systems, finding spatial variations in both magnetic fields and
inferred currents flowing north-south that are common to both systems. With the
greatly expanded coverage of the equatorial plane achieved during the latter
years of the mission, we are able to present a complete survey of dawn-dusk and
day-night asymmetries in the structure of the oscillating fields and currents.
We show that the general structure of the rotating currents is simpler than
previously reported, and that the relatively enhanced nightside equatorial
fields and currents are due in part to related periodic vertical motion of
Saturn's magnetotail current sheet.
