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 ∇ × B throughout the magnetosphere, thus permitting the first global mapping of Saturn's currents in three dimensions. The azimuthal ring current J ϕ 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 ϕ also has a noticeable local time asymmetry, being the largest in the midnight and dawn sectors. The meridional currents J ρ 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.