Science · 6 pages · 12 min
Why magnetic north is not geographic north
Geographic north is the spin axis, and magnetic north is where the field points.
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From the opening
Magnetic north is not geographic north because Earth's magnetic field is not lined up with its rotation axis. Geographic north is where the meridians meet, the pole of the spin, while a compass follows a field whose magnetic pole sits elsewhere and moves. The opening covers spin pole versus magnetic pole, why the core need not align them, and how declination is the local angle.
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Inside
- Spin pole versus magnetic pole
- Why the core need not align them
- How declination is the local angle
- Why a reversal is not a flipped Earth
- Where the idea stops applying
- A distinction worth keeping
Sources
- The geomagnetic dynamo and the offset dipole
- Magnetic poles versus the geographic poles