This picture is from a model of how the earth's magnetic field is generated.
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Glaztmeir and Roberts of LANL
The Generation of Jupiter's Magnetosphere
Magnetospheres are generated with 1.) magnetic materials and 2.) with motions within the magnetic material.
The terrestrial planets generate magnetospheres within the iron cores at the center. This leads to dipole-shaped, rounded magnetic fields. Jupiter has almost no iron core, certainly not a large enough one to be responsible for it's enormous magnetic field.
The magnetic material of Jupiter is found within the liquid metallic shell found within Jupiter. Motions within that shell produce magnetic field. Because these currents are generated within a shell, they produces a magnetic field with a much stronger quadrupole-component. The quadrupole component contributes to making Jupiter's magnetic field more pointed and bullet-shaped.
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