Editing Magnetohydrodynamics (section)

=== Geophysics ===
Beneath the Earth's mantle lies the core, which is made up of two parts: the solid inner core and liquid outer core.<ref>{{cite web | url=https://www.livescience.com/39780-magnetic-field-pushes-earth-core.html | title=Why Earth's Inner and Outer Cores Rotate in Opposite Directions | website=[[Live Science]] | date=19 September 2013 }}</ref><ref>{{cite web | url=https://www.pnas.org/post/journal-club/earths-contrasting-inner-core-rotation-and-magnetic-field-rotation-linked | title=Earth's contrasting inner core rotation and magnetic field rotation linked | date=7 October 2013 }}</ref> Both have significant quantities of [[iron]]. The liquid outer core moves in the presence of the magnetic field and eddies are set up into the same due to the [[Coriolis effect]].<ref>{{cite web | url=http://ffden-2.phys.uaf.edu/webproj/647_fall_2019/Stefan_Awender/GFDwebsite/fluid_dynamics_core.html | title=Geodynamo }}</ref> These eddies develop a magnetic field which boosts Earth's original magnetic field—a process which is self-sustaining and is called the geomagnetic dynamo.<ref name = "pbs">[https://www.pbs.org/wgbh/nova/magnetic/reve-drives.html NOVA | Magnetic Storm | What Drives Earth's Magnetic Field? | PBS<!-- Bot generated title -->]</ref>

[[File:NASA 54559main comparison1 strip.gif|thumb|center|350px|Reversals of [[Earth's magnetic field]]]]

Based on the MHD equations, Glatzmaier and Paul Roberts have made a supercomputer model of the Earth's interior. After running the simulations for thousands of years in virtual time, the changes in Earth's magnetic field can be studied. The simulation results are in good agreement with the observations as the simulations have correctly predicted that the Earth's magnetic field flips every few hundred thousand years. During the flips, the magnetic field does not vanish altogether—it just gets more complex.<ref name = "glatz">[https://science.nasa.gov/science-news/science-at-nasa/2003/29dec_magneticfield/ Earth's Inconstant Magnetic Field – NASA Science<!-- Bot generated title -->]</ref>

====Earthquakes====
Some monitoring stations have reported that [[earthquakes]] are sometimes preceded by a spike in [[ultra low frequency]] (ULF) activity.  A remarkable example of this occurred before the [[1989 Loma Prieta earthquake]] in [[California]],<ref>{{cite journal |first1=Antony C. |last1=Fraser-Smith |first2=A. |last2=Bernardi |first3=P. R. |last3=McGill |first4=M. E. |last4=Ladd |first5=R. A. |last5=Helliwell |first6=O. G. |last6=Villard Jr. |date=August 1990 |title=Low-Frequency Magnetic Field Measurements Near the Epicenter of the M<sub>s</sub> 7.1 Loma Prieta Earthquake |journal=[[Geophysical Research Letters]] |volume=17 |issue=9 |pages=1465–1468 |issn=0094-8276 |oclc=1795290 |access-date=December 18, 2010 |url=http://ee.stanford.edu/~acfs/LomaPrietaPaper.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://ee.stanford.edu/~acfs/LomaPrietaPaper.pdf |archive-date=2022-10-09 |url-status=live |doi=10.1029/GL017i009p01465 |bibcode=1990GeoRL..17.1465F}}</ref> although a subsequent study indicates that this was little more than a sensor malfunction.<ref>{{Cite journal | last1 = Thomas | first1 = J. N. | last2 = Love | first2 = J. J. | last3 = Johnston | first3 = M. J. S. | title = On the reported magnetic precursor of the 1989 Loma Prieta earthquake | doi = 10.1016/j.pepi.2008.11.014 | journal = Physics of the Earth and Planetary Interiors | volume = 173 | issue = 3–4 | pages = 207–215 |date=April 2009 | bibcode=2009PEPI..173..207T}}</ref> On December 9, 2010, geoscientists announced that the [[Demeter (satellite)|DEMETER]] satellite observed a dramatic increase in ULF radio waves over [[Haiti]] in the month before the magnitude 7.0&nbsp;M<sub>w</sub> [[2010 Haiti earthquake|2010 earthquake]].<ref>{{cite web|url=http://www.technologyreview.com/blog/arxiv/26114/|title=Spacecraft Saw ULF Radio Emissions over Haiti before January Quake|author=KentuckyFC <!-- blogger's legitimate nom de plume -->|date=December 9, 2010|website=Physics arXiv Blog|publisher=[[TechnologyReview.com]]|location=[[Cambridge, Massachusetts]]|access-date=December 18, 2010}}  {{Cite journal|last1=Athanasiou|first1=M|last2=Anagnostopoulos|first2=G|last3=Iliopoulos|first3=A|last4=Pavlos|first4=G|last5=David|first5=K|year=2010|title=Enhanced ULF radiation observed by DEMETER two months around the strong 2010 Haiti earthquake|journal=Natural Hazards and Earth System Sciences|volume=11|issue=4|pages=1091|arxiv=1012.1533|doi=10.5194/nhess-11-1091-2011|bibcode=2011NHESS..11.1091A|s2cid=53456663|doi-access=free}}</ref> Researchers are attempting to learn more about this correlation to find out whether this method can be used as part of an early warning system for earthquakes.