Which process in the outer core contributes to Earth's magnetic field?

Which process in the outer core contributes to Earth's magnetic field?

• A. The movement of liquid iron in the outer core generates the field.
• B. Solid iron in the inner core generates the field.
• C. The crust's magnetization generates the field.
• D. Solar radiation generates the field.

Answer: (A)

The main idea is the geodynamo: Earth's magnetic field is produced by the flowing, electrically conducting liquid iron in the outer core. Heat and composition differences drive convection in this molten iron, and the planet’s rotation twists these motions. The combination of moving charges and rotation creates electric currents, and those currents generate a magnetic field that threads out to the surface. The inner core is solid iron and doesn’t flow like the outer core does, so it doesn’t by itself produce the ongoing magnetic field through dynamo action. The crust’s magnetization is remanent, meaning rocks locked in past magnetic fields rather than actively generating the current field. Solar radiation doesn’t create Earth’s magnetic field either; it can shape the magnetosphere, but the field itself comes from the dynamo action in the outer core.

The main idea is the geodynamo: Earth's magnetic field is produced by the flowing, electrically conducting liquid iron in the outer core. Heat and composition differences drive convection in this molten iron, and the planet’s rotation twists these motions. The combination of moving charges and rotation creates electric currents, and those currents generate a magnetic field that threads out to the surface.

The inner core is solid iron and doesn’t flow like the outer core does, so it doesn’t by itself produce the ongoing magnetic field through dynamo action. The crust’s magnetization is remanent, meaning rocks locked in past magnetic fields rather than actively generating the current field. Solar radiation doesn’t create Earth’s magnetic field either; it can shape the magnetosphere, but the field itself comes from the dynamo action in the outer core.