[AndroidNeox (OP)]

None of the explanations I've heard explain Earth's magnetic field. The field originates in the core where the temperature is well over the Curie temperature so the iron and nickel are non-magnetic. There is a metallic flow but that won't produce a magnetic field, either.

There must be charge separation and electrical current. Are there any physical models that explain this current?

[diverjohn]

The magnetic field is made in the region between the core and the mantle, where the iron-nickel material moves and thus the magnetic field is created. About the Curie Effect: applying sufficient heat to a regular iron magnet will allow the magnetic domains to move toward random positions and thus reduce the magnetic field. Why does earth's molten iron still have magnetic properties then? Likely because there is so much iron below the mantel that the amount lost by heat is not 100%.

[AndroidNeox (OP)]

the iron-nickel material moves and thus the magnetic field is created

No, movement of iron and/or nickel won't produce a magnetic field in liquid form any more than it does when they are solid. There must be net charge motion.

[guest45734]

None of the explanations I've heard explain Earth's magnetic field. The field originates in the core where the temperature is well over the Curie temperature so the iron and nickel are non-magnetic. There is a metallic flow but that won't produce a magnetic field, either.

There must be charge separation and electrical current. Are there any physical models that explain this current?

The interesting thing is the earths core flipping every few thousands of years, currently the pole is on average moving to siberia at about 5 to 10 miles per year. Under dynamo theory "The Earth's magnetic field is believed to be generated by electric currents in the conductive material of its core, created by convection currents due to heat escaping from the core. However the process is complex, and computer models that reproduce some of its features have only been developed in the last few decades"
see attached link https://en.wikipedia.org/wiki/Earth%27s_magnetic_field#Magnetic_field_reversals

[evan_au]

There is a metallic flow but that won't produce a magnetic field, either.

The energy source is the heat released by the liquid outer core slowly solidifying, causing the solid inner core to slowly expand over time. This heat release causes convection currents in the liquid outer core.

The magnetic field itself is produced by electrical currents in the liquid nickel/iron, produced by magnetohydrodynamic effects.

In laboratory experiments, two additional factors are needed to kick-start the dynamo:
- Differential rotation of Earth's solid inner core and the mantle
- a "seed" magnetic field (that may have come from the solar magnetic field?)

These effects have been reproduced in the lab using a model with liquid sodium instead of liquid iron. One of the more recent experiments is described here:

the temperature is well over the Curie temperature so the iron and nickel are non-magnetic.

Sodium is not ferromagnetic, and yet the effects are reproducible in the laboratory because the metallic flow and electrical currents are similar (just faster).

The Sun also displays a magnetic field -  the Sun is composed mostly of a plasma of Hydrogen and Helium; these elements aren't ferromagnetic either.

[AndroidNeox (OP)]

The magnetic field itself is produced by electrical currents in the liquid nickel/iron, produced by magnetohydrodynamic effects.

Thanks. This is the key piece of information left out of every explanation I've heard.