Earth's magnetic field
Protects Earth from solar wind and enables navigation.
Earth's magnetic field, or geomagnetic field, originates deep within the planet, generated by electric currents produced by the motion of convection currents in the outer core, which consists of a mixture of molten iron and nickel. These currents are driven by heat escaping from the core in a process known as a geodynamo. The field extends from Earth's interior far into space, where it interacts with the solar wind, a stream of charged particles from the Sun. This interaction creates the magnetosphere, a region that extends tens of thousands of kilometres into space and protects Earth by deflecting most of the solar wind and cosmic rays, which would otherwise strip away the upper atmosphere, including the ozone layer that shields the planet from harmful ultraviolet radiation. The field’s magnitude varies across the surface and changes over time; in a survey from 2019, it ranged around specific values, with a minimum intensity in the South Atlantic Anomaly over South America and maxima over northern Canada, Siberia, and the coast of Antarctica south of Australia. For approximation, the field behaves like a magnetic dipole tilted at about 11° relative to Earth’s rotational axis, as if a giant bar magnet were placed at that angle through the center. The North geomagnetic pole, located on Ellesmere Island in Nunavut, Canada, actually corresponds to the South pole of the magnetic field, while the South geomagnetic pole corresponds to the north pole, because opposite poles attract and a compass needle’s north end points toward the magnetic South. These poles slowly move over geological time, but at irregular intervals averaging several hundred thousand years, the field reverses, abruptly swapping the North and South Magnetic Poles. Such reversals are recorded in igneous rocks, creating detectable stripes centered on mid-ocean ridges where seafloor spreads, and they allow paleomagnetists to study past geomagnetic fields, continental motions, and ocean floor movements. Humans have used compasses for direction since the 11th century and for navigation since the 12th, while many organisms, from bacteria to pigeons, use magnetoreception for orientation.
- field
- Geophysics, Paleomagnetism
- known_for
- Deflecting solar wind, enabling compass navigation, recording magnetic reversals in rocks
- dipole_tilt
- Approximately 11° with respect to Earth's rotational axis
- pole_migration
- North Magnetic Pole moves up to 40 km per year; has migrated northwestward over the last 180 years
Lore & Background
Earth's magnetic field, or geomagnetic field, extends from the planet's interior into space, where it interacts with the solar wind. It is generated by electric currents arising from the motion of convection currents of molten iron and nickel in the outer core, a process called a geodynamo driven by heat escaping the core. The field is approximated as a magnetic dipole tilted about 11° from Earth's rotational axis, as if a bar magnet were placed at that angle through the center. The North geomagnetic pole (on Ellesmere Island, Nunavut, Canada) corresponds to the magnetic field's south pole, and the South geomagnetic pole to its north pole, because opposite poles attract and a compass needle's north end points toward the magnetic south. The field's magnitude varies across the surface and over time; a 2019 survey recorded values from about 30000 to 60000 nT. The magnetosphere, the region of space dominated by this field, extends tens of thousands of kilometers above the ionosphere, protecting Earth from charged solar particles and cosmic rays that would otherwise strip away the upper atmosphere and ozone layer. The field slowly shifts over geological timescales, and at irregular intervals averaging several hundred thousand years, it reverses, swapping the magnetic poles. These reversals are recorded in rocks, aiding paleomagnetists in studying past geomagnetic fields, continental motions, and ocean floor spreading. Humans have used compasses for direction since the 11th century and for navigation since the 12th, while many organisms, from bacteria to pigeons, use magnetoreception for orientation.
Reader's Guide
The significance of Earth's magnetic field lies in its role as a protective shield and a navigational aid. It deflects most of the solar wind, whose charged particles would otherwise strip away the ozone layer that protects Earth from harmful ultraviolet radiation. Calculations of the loss of carbon dioxide from Mars's atmosphere indicate that the dissipation of its magnetic field caused a near total loss of its atmosphere. The field also records its own history: reversals of the geomagnetic poles leave a record in rocks, valuable for paleomagnetists in calculating past geomagnetic fields and studying the motions of continents and ocean floors. Humans have used compasses for direction finding since the 11th century A.D. and for navigation since the 12th century. Various organisms, from bacteria to pigeons, use magnetoreception for orientation and navigation.
Did You Know?
- The North geomagnetic pole (on Ellesmere Island, Nunavut, Canada) actually represents the South pole of Earth's magnetic field.
- At irregular intervals averaging several hundred thousand years, Earth's field reverses and the North and South Magnetic Poles abruptly switch places.
Frequently Asked Questions
Who is Earth's magnetic field?
Earth's magnetic field is the invisible magnetic shield that stretches from the planet's molten outer core out into space, where it meets the solar wind. It is produced by the churning of liquid iron and nickel in the outer core, a process geologists call the geodynamo.
What are Earth's magnetic field's powers/role?
Its primary job is deflecting the charged particles of the solar wind away from the planet, shielding the upper atmosphere and ozone layer from being stripped away. It also gives compass needles a direction to align with, enabling magnetic navigation.
How does Earth's magnetic field's story end?
It has no fixed ending—the field is in constant motion, with the North Magnetic Pole drifting up to 40 km per year in a northwestward trend over the past 180 years. Rocks also record full magnetic reversals, so the narrative keeps rewriting itself across geological time.
Why is Earth's magnetic field important?
Without it, the solar wind would erode the upper atmosphere and destroy the ozone layer, leaving surface life far more exposed to harmful radiation. It also underpins paleomagnetism, allowing scientists to read the magnetic history locked into ancient rock formations.
More in Geology 1-24
Spotted an error? Know more?
This is a living reference — every entry is fact-audited, and reader corrections feed straight into our audit queue. Suggest an edit · See this site's audit record