The Magnetic Field of Neptune
Neptune's magnetic field is tilted 47 from the planet's rotation axis and is offset at least 0.55 radii, about 8,500 mi (13,500 km) from the physical center. The dynamo electric currents produced within the planet, therefore, must be relatively closer to the surface than for Earth, Jupiter, or Saturn. Because of its unusual orientation, and the tilt of the planet's rotation axis, Neptune's magnetic field goes through dramatic changes as the planet rotates in the solar wind.
Voyager's planetary radio astronomy instrument measured the periodic radio waves generated by the magnetic field and determined that the rotation rate of the interior of Neptune is 16 hours and 7 minutes.
Voyager also detected auroras, similar to the northern and southern lights on Earth, in Neptune's atmosphere. Unlike those on Earth, due to Neptune's complex magnetic field, the auroras are extremely complicated processes that occur over wide regions of the planet, not just near the planet's magnetic poles.