Earth's magnetic field

Earth's magnetic field is the magnetic field surrounding the planet, generated mainly by motion of electrically conducting liquid iron in its outer core. It varies over time and shields Earth from much of the solar wind.

Geodynamo: The process by which motion in a planet's electrically conducting fluid generates and sustains a magnetic field. Convection and Earth's rotation drive the process that generates the field.
Magnetic field: A physical field that exerts magnetic forces on moving electric charges and magnetic materials. Earth's field is one planetary example of this broader physical phenomenon.
Compass: A navigational instrument whose magnetized needle aligns with a magnetic field. A compass uses the horizontal direction of Earth's field to indicate magnetic north.
Aurora: Light produced when energetic charged particles excite gases in a planet's upper atmosphere. Earth's field guides many charged particles toward polar regions where auroras form.
Earth's outer core: The liquid iron-rich layer between Earth's solid inner core and rocky mantle. Its moving conductive fluid supplies the currents that sustain the field.
Magnetic pole: A region where a magnetic field points vertically into or out of a surface. The field's north and south poles are defined by its direction at Earth's surface.
Paleomagnetism: The study of the record of Earth's ancient magnetic field preserved in rocks and sediments. Magnetic minerals preserve past field directions and polarity.
South Atlantic Anomaly: A region over the South Atlantic where Earth's magnetic field is unusually weak at satellite altitudes. It shows that the field's strength varies substantially across the planet.
Magnetic dipole: A magnetic field pattern resembling that of a small bar magnet, with two opposite poles. Earth's field is dominated by a dipole component, though it is not a perfect bar-magnet field.
Magnetic declination: The angle between magnetic north and geographic north at a location. It describes how a compass direction differs from true north.

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