The discussion centers on the generation of a magnetic field by the Earth's neutral outer core, which is convective and conductive. Participants clarify that while the outer core is charge-neutral, it can still produce a magnetic field due to the movement of mobile electrons, similar to a current-carrying wire. The conversation references Maxwell's Equations and the phenomenon of charge separation in conductive liquids, suggesting that even a weak magnetic field can lead to significant magnetic field generation under specific conditions, such as in experiments with stirred liquid sodium.
PREREQUISITESPhysicists, geophysicists, and students interested in electromagnetism and planetary science will benefit from this discussion, particularly those exploring the dynamics of Earth's core and magnetic field generation.
A current-carrying wire is charge-neutral, nevertheless it generates a magnetic field. Its negative charges (mobile electrons) move, but the equal amount of positive charge (metallic ions) does not.AustinLee said:Even if the outer core is convecting and conductive it is still charge neutral, so how can a Magnetic field be generated?
Okay I can understand the neutrality. However does that mean the Earth's outer core has a electrical current?jtbell said:A current-carrying wire is charge-neutral, nevertheless it generates a magnetic field. Its negative charges (mobile electrons) move, but the equal amount of positive charge (metallic ions) does not.
AustinLee said:However does that mean the Earth's outer core has a electrical current?
So let's assume there is a magnetic field (maybe much weaker than the magnetic field of earth) and a neutral conductive liquid is moving in this field. Then there will be some charge separation as the electrons and nuclear charges are deflected in different directions. The amount of charge built up will be limited by the build up of an electric field till some equilibrium is reached. Nevertheless the speed of negative and positive charges may be different thus leading to an additional magnetic field. If oriented parallel to the original field, this can lead to a rapid build up of a strong magentic field starting from a small random field fluctuation.AustinLee said:Even if the outer core is convecting and conductive it is still charge neutral, so how can a Magnetic field be generated? Maxwells Equation say there needs to be net charge moving for a Magnetic field to be generated.