I did a search on jupiters polarisation and came up with many results. Looks like either circular or eliptical. Heres a shameless cut and paste from one site....
Observations of Jupiter made at the Owens Valley Radio Observatory with wavelengths of 10 and 21 cm indicate that the radiation has a small and variable circularly-polarized component which has a more distinct double structure than the rest of the radiation. The maximum degree of circular polarization is about 4%, and the variation is correlated with Jupiter's rotation. From the measurements it is shown that the polarity of Jupiter's magnetic field is opposite that of the earth's and that the field strength at 2.5 radii from the center of the planet in the equatorial plane is 1.7 gauss with a very large uncertainty. (Author)
Baz
