Q.The magnetic field of Earth can be modelled by that of a point dipole placed at the centre of the Earth. The dipole axis makes an angle of $11.3^\circ$ with the axis of Earth. At Mumbai, declination is nearly zero. Then,

Earth's Magnetism – A First Look

Imagine you're holding a small compass. No matter where you stand on Earth, the needle always settles pointing roughly north-south. That needle is aligning itself with a magnetic field that surrounds the entire planet. Earth behaves as if a giant bar magnet were buried deep inside it, with its south pole near the geographic north pole and its north pole near the geographic south pole.

Why does this happen? Deep in Earth's outer core, molten iron and nickel are in constant, churning motion. This flow of liquid metal, driven by heat from the inner core and Earth's rotation, acts like a giant dynamo — it generates electric currents, and those currents produce a magnetic field. This is called the geodynamo effect.

The field is not perfectly aligned with Earth's spin axis. It's tilted by about 11.5°, and it drifts slowly over time. That's why a compass doesn't point exactly to true geographic north — it points to magnetic north.

---

The Three Elements of Earth's Magnetic Field …