The magnetic fields of the Ice Giant Planets Uranus and Neptune (U/N) are unique in the solar system. Based on a substantial database measured on Earth for representative planetary fluids at representative dynamic pressures up to 200 GPa (2 Mbar) and a few 1000 K, the complex magnetic fields of U/N are (i) probably made primarily by degenerate metallic fluid H (MFH) at or near the crossover from the H-He envelopes to Ice cores at ~100 GPa (Mbar) pressures and normalized radii of ~90% of the radii of U/N; (ii) because those magnetic fields are made relatively close to the surfaces of U/N, non-dipolar fields can be expected; (iii) the Ice cores are most probably a heterogeneous fluid mixture of H, N, O, C, Fe/Ni and silicate-oxides and their mutual reaction products at high pressures and temperatures,as discussed elsewhere. Ironically, there is probably little nebular Ice in the Ice Giant Planets.
@article{arxiv.1503.01042,
title = {Magnetic Fields of Uranus and Neptune: Metallic Fluid Hydrogen},
author = {W. J. Nellis},
journal= {arXiv preprint arXiv:1503.01042},
year = {2015}
}