What is the primary source of Earth’s magnetic field?

• A. Electric currents generated by convection and rotation in Earth’s liquid outer core (the geodynamo)
• B. A giant permanent magnet located at Earth’s geographic North Pole
• C. The magnetic field of the Sun directly inducing Earth’s field
• D. Magnetized iron in Earth’s crust producing a global field

Answer: (A)

Verified step by step guidance

1. Understand that Earth's magnetic field is generated internally, not by external sources like the Sun or surface rocks.
2. Recognize that the Earth’s outer core is composed of liquid iron and nickel, which are conductive materials capable of carrying electric currents.
3. Learn that the motion of this liquid metal, driven by convection currents due to heat escaping from the inner core and influenced by Earth's rotation, creates electric currents.
4. These electric currents produce a magnetic field through a process known as the geodynamo, which sustains Earth's magnetic field over time.
5. Conclude that the primary source of Earth's magnetic field is the electric currents generated by convection and rotation in the liquid outer core, rather than a permanent magnet or external magnetic influences.