Editing Earth's magnetic field (section)

==== Global models ====
The [[International Association of Geomagnetism and Aeronomy]] maintains a standard global field model called the [[International Geomagnetic Reference Field]] (IGRF). It is updated every five years. The 11th-generation model, IGRF11, was developed using data from satellites ([[Ørsted (satellite)|Ørsted]], [[CHAMP (satellite)|CHAMP]] and SAC-C) and a world network of geomagnetic observatories.<ref>{{cite journal|last1=Finlay|first1=CC|last2=Maus|first2=S|last3=Beggan|first3=CD|last4=Hamoudi|first4=M.|last5=Lowes|first5=FJ|last6=Olsen|first6=N|last7=Thébault|first7=E.|date=2010|title=Evaluation of candidate geomagnetic field models for IGRF-11|journal=Earth, Planets and Space|volume=62|issue=10|pages=787–804|bibcode=2010EP&S...62..787F|doi=10.5047/eps.2010.11.005|s2cid=530534|doi-access=free}}</ref> The spherical harmonic expansion was truncated at degree 10, with 120 coefficients, until 2000. Subsequent models are truncated at degree 13 (195 coefficients).<ref name=irgf_health>{{cite web |url=https://www.ncei.noaa.gov/products/international-geomagnetic-reference-field/health-warning |title=The International Geomagnetic Reference Field: A "Health" Warning |date=January 2010 |publisher=National Geophysical Data Center |access-date=13 October 2011}}</ref>

Another global field model, called the [[World Magnetic Model]], is produced jointly by the United States [[National Centers for Environmental Information]] (formerly the National Geophysical Data Center) and the [[British Geological Survey]]. This model truncates at degree 12 (168 coefficients) with an approximate spatial resolution of 3,000&nbsp;kilometers. It is the model used by the [[United States Department of Defense]], the [[Ministry of Defence (United Kingdom)]], the United States [[Federal Aviation Administration]] (FAA), the [[North Atlantic Treaty Organization]] (NATO), and the [[International Hydrographic Organization]] as well as in many civilian navigation systems.<ref>{{cite web |title=The World Magnetic Model |url=https://www.ncei.noaa.gov/products/world-magnetic-model |publisher=National Geophysical Data Center |access-date=14 October 2011}}</ref>

The above models only take into account the "main field" at the core-mantle boundary. Although generally good enough for navigation, higher-accuracy use cases require smaller-scale [[magnetic anomalies]] and other variations to be considered. Some examples are (see geomag.us ref for more):<ref>{{cite web |title=Geomagnetic and Electric Field Models |url=https://geomag.us/models/index.html |website=geomag.us}}</ref>
* The "comprehensive modeling" (CM) approach by the [[Goddard Space Flight Center]] ([[NASA]] and [[GSFC]]) and the [[Danish Space Research Institute]]. CM attempts to reconcile data with greatly varying temporal and spatial resolution from ground and satellite sources. The latest version as of 2022 is CM5 of 2016. It provides separate components for main field plus [[lithosphere]] (crustal), [[Tide#Principal lunar semi-diurnal constituent|M2 tidal]], and primary/induced magnetosphere/ionosphere variations.<ref>{{cite web |title=Model information |url=https://ccmc.gsfc.nasa.gov/models/modelinfo.php?model=CM5 |website=ccmc.gsfc.nasa.gov |access-date=2022-01-12 |archive-date=2021-12-09 |archive-url=https://web.archive.org/web/20211209100224/https://ccmc.gsfc.nasa.gov/models/modelinfo.php?model=CM5 |url-status=dead }}</ref>
* The US [[National Centers for Environmental Information]] developed the [[Enhanced Magnetic Model]] (EMM), which extends to degree and order 790 and resolves [[magnetic anomalies]] down to a wavelength of 56&nbsp;kilometers. It was compiled from satellite, marine, aeromagnetic and ground magnetic surveys. {{As of|2018}}, the latest version, EMM2017, includes data from The European Space Agency's Swarm satellite mission.<ref>{{cite web |title=The Enhanced Magnetic Model|url=https://www.ncei.noaa.gov/products/enhanced-magnetic-model |publisher=United States [[National Centers for Environmental Information]] |access-date=29 June 2018}}</ref>

For historical data about the main field, the IGRF may be used back to year 1900.<ref name="irgf_health" /> A specialized GUFM1 model estimates back to year 1590 using ship's logs.<ref>{{cite journal |last1=Jackson |first1=Andrew |last2=Jonkers |first2=Art R. T. |last3=Walker |first3=Matthew R. |title=Four centuries of geomagnetic secular variation from historical records |journal=Philosophical Transactions of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences |date=15 March 2000 |volume=358 |issue=1768 |pages=957–990 |doi=10.1098/rsta.2000.0569 |bibcode=2000RSPTA.358..957J |s2cid=40510741}}</ref> [[Paleomagnetic]] research has produced models dating back to 10,000&nbsp;BCE.<ref>{{cite web |title=The GEOMAGIA database |url=https://geomagia.gfz-potsdam.de/models.php |website=geomagia.gfz-potsdam.de}}</ref>