Evidence for the unexpected time-stable symmetry of the Jovian magnetosphere

The assumption of axial symmetry provides a first-order approximation to the true magnetospheric configuration of Jupiter out to a few Jovian radii. Decimetric radio observations of Parkes and the Pioneer 10 magnetometer results suggest that planar (or mirror image) symmetry provides a better approximation; the radio results indicate a configuration that has not measurably changed over one 12-year orbital period of Jupiter.