Editing Earth's magnetic field (section)

=== Intensity ===
The intensity of the field is often measured in [[Gauss (unit)|gauss (G)]], but is generally reported in [[Tesla (unit)|microteslas]] (μT), with 1&nbsp;G = 100&nbsp;μT. A nanotesla is also referred to as a gamma (γ). The Earth's field ranges between approximately {{cvt|22 and 67|μT|G}}.<ref>{{Cite web |title=An Overview of the Earth's Magnetic Field |url=http://www.geomag.bgs.ac.uk/education/earthmag.html#_Toc2075549 |access-date=2024-03-02 |website=www.geomag.bgs.ac.uk}}</ref> By comparison, a strong [[refrigerator magnet]] has a field of about {{cvt|10000|μT|G}}.<ref>{{cite web |url=http://www.magnet.fsu.edu/education/tutorials/magnetminute/tesla-transcript.html |last1=Palm |first1=Eric |title=Tesla |publisher=National High Magnetic Field Laboratory |year=2011 |access-date=20 October 2013 |archive-url=https://web.archive.org/web/20130321234403/http://www.magnet.fsu.edu/education/tutorials/magnetminute/tesla-transcript.html |archive-date=21 March 2013 |url-status=dead }}</ref>

A map of intensity contours is called an ''isodynamic chart''. As the [[#Geographical variation|World Magnetic Model]] shows, the intensity tends to decrease from the poles to the equator. A minimum intensity occurs in the [[South Atlantic Anomaly]] over South America while there are maxima over northern Canada, Siberia, and the coast of Antarctica south of Australia.<ref name="renamed_from_2010_on_20131022170733" />

The intensity of the magnetic field is subject to change over time. A 2021 paleomagnetic study from the [[University of Liverpool]] contributed to a growing body of evidence that the Earth's magnetic field cycles with intensity every 200 million years. The lead author stated that "Our findings, when considered alongside the existing datasets, support the existence of an approximately 200-million-year-long cycle in the strength of the Earth's magnetic field related to deep Earth processes."<ref>{{Cite web|date=2021-08-31|title=Ancient lava reveals secrets of Earth's magnetic field cycle|url=https://cosmosmagazine.com/science/ancient-lava-reveals-secrets-of-earths-magnetic-field-cycle/|access-date=2021-09-03|website=Cosmos Magazine|language=en-AU}}</ref>