View source for The Science of Earths Magnetic Field and Geomagnetism

== Introduction ==
Geomagnetism is the study of the Earth's [[Magnetic Field|Magnetic Field]], a natural phenomenon that extends from the Earth's interior into space, where it interacts with the solar wind, a stream of charged particles emanating from the Sun. Its magnitude at the Earth's surface ranges from 25 to 65 microteslas (0.25 to 0.65 gauss). It is approximately the field of a magnetic dipole currently tilted at an angle of about 11 degrees with respect to Earth's rotational axis, as if there were a bar magnet placed at that angle at the center of the Earth. However, unlike the field of a bar magnet, Earth's field changes over time because it is generated by a geodynamo (in Earth's outer core).

== Earth's Magnetic Field ==
The Earth's magnetic field is primarily a geocentric axial dipole, with the North and South poles located near the Earth's geographic poles. As such, the field is similar to that of a bar magnet, but this similarity is superficial. The magnetic field is generated by electric currents due to the motion of convection currents of molten iron in the Earth's outer core driven by heat escaping from the core, a natural process referred to as a [[Geodynamo|geodynamo]].

[[Image:Detail-40499.jpg|thumb|center|A photograph of a model of the Earth's core, showing the outer core (in orange), where the geodynamo that generates the Earth's magnetic field is located.|class=only_on_mobile]]
[[Image:Detail-40500.jpg|thumb|center|A photograph of a model of the Earth's core, showing the outer core (in orange), where the geodynamo that generates the Earth's magnetic field is located.|class=only_on_desktop]]

The Earth's magnetic field strength was measured by Carl Friedrich Gauss in 1832 and has been repeatedly measured since then, showing a relative decay of about 10% over the last 150 years. The Magsat satellite and subsequent satellites have discovered a region of intense magnetic field in the Earth's crust at the South Atlantic Anomaly.

== Geomagnetism ==
Geomagnetism is the study of the Earth's magnetic field in space and its interactions with entities that penetrate it. The Earth's magnetic field, which approximates a dipolar field, varies significantly in intensity, direction, and variation over time and geographical locations.

The Earth's magnetic field shields the Earth from the charged particles of the solar wind and cosmic rays that would otherwise strip away the upper atmosphere, including the ozone layer that protects the Earth from harmful ultraviolet radiation. It is mostly generated in the fluid outer core of the Earth where convective motion of molten iron generates electric currents. The magnetic field is also generated to a lesser extent by electric currents in the air due to solar radiation.

== Magnetic Poles ==
The Earth's magnetic field is defined by the North and South poles that align generally with the geographic poles. The North Magnetic Pole wanders, but generally maintains a lagging position to the Earth's axial rotation. The South Magnetic Pole mirrors the North Magnetic Pole. The Earth's magnetic field is currently undergoing a reversal where the North and South Magnetic Poles are switching places.

== Geomagnetic Reversals ==
The Earth's magnetic field has undergone numerous reversals of polarity. A geomagnetic reversal is a change in the Earth's magnetic field such that the positions of magnetic north and magnetic south are interchanged. The Earth's field has alternated between periods of normal polarity, in which the direction of the field was the same as the present direction, and reverse polarity, in which the field was in the opposite direction. These periods are known as chrons.

== Conclusion ==
The Earth's magnetic field is a complex and dynamic phenomenon that is crucial for life on Earth. It shields the planet from harmful solar radiation, aids in navigation for humans and animals, and plays a key role in our planet's climate. The study of geomagnetism is a critical aspect of Earth science, helping us understand not only our own planet but also the broader universe.

== See Also ==
* [[Geomagnetic Storm|Geomagnetic Storms]]
* [[Magnetosphere|Magnetosphere]]
* [[Solar Wind|Solar Wind]]

[[Category:Earth Science]]
[[Category:Geomagnetism]]
[[Category:Magnetic Field]]
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