Geomagnetic reversal

A geomagnetic reversal is a change in Earth’s magnetic field in which magnetic north and south exchange polarity. The field weakens and becomes complex during the transition, which can take thousands of years.

Geodynamo: The process by which motion in a planet’s electrically conducting fluid generates a magnetic field. Convection and rotation in Earth’s outer core generate the field whose polarity can reverse.
Brunhes–Matuyama reversal: The geomagnetic reversal about 780,000 years ago that ended the Matuyama reversed chron and began the Brunhes normal chron. It is the most recent full reversal and a major boundary in the geomagnetic polarity timescale.
Magnetic declination: The angle between geographic north and the direction a compass points horizontally. Declination is one component of the directional measurements used to reconstruct past field orientations.
Magnetosphere: The region around Earth in which its magnetic field shapes the motion of charged particles. A weakened, changing field modifies the structure and extent of this protective region.
Earth's outer core: Earth’s liquid iron-rich layer between the solid inner core and the mantle. Its moving, electrically conducting fluid drives the changing magnetic field.
Matuyama reversed chron: A long interval of reversed geomagnetic polarity lasting from about 2.58 million to 780,000 years ago. Its end marks the most recent completed polarity reversal.
Magnetic inclination: The angle between a magnetic field direction and the horizontal plane. Its sign and magnitude help identify the polarity recorded by rocks.
Aurora: Light emitted in the upper atmosphere when energetic charged particles excite atmospheric atoms and molecules. A less orderly field could change where charged particles enter the atmosphere and auroras occur.
Magnetic field: A region in which magnetic forces act on moving charges and magnetic materials. A reversal changes the global field’s polarity, not the existence of magnetism itself.
Cretaceous Normal Superchron: An interval of predominantly normal geomagnetic polarity from about 121 to 83 million years ago. Its extended lack of reversals contrasts with periods of frequent polarity changes.

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