Three-Dimensional Currents in Saturn's Magnetosphere

Observations of Saturn's magnetic field from July 2004 to December 2016 have been combined to allow a numerical calculation of del x B throughout the magnetosphere, thus permitting the first global mapping of Saturn's currents in three dimensions. The azimuthal ring current J(phi) dominates the magnetospheric currents, peaking near the orbit of the moon Rhea and having a total magnitude of over 10 mega-Amperes integrated within the L-shell of Titan. In meridional cross section, the ring current has a teardrop shape rather than a block shape. J(phi) also has a noticeable local time asymmetry, being the largest in the midnight and dawn sectors. The meridional currents J(rho) and J(z) are smaller than the ring current by an order of magnitude; they flow radially outward near the equator and return at higher latitudes in a looping pattern reminiscent of Hadley cell atmospheric convection. There are two such loops: one in the northern hemisphere and one in the south, flowing in opposing directions. In the noon sector, a strong J(z) current may indicate the dayside cusp.