Editing Geomagnetic storm (section)

== History of the theory ==
In 1930, [[Sydney Chapman (mathematician)|Sydney Chapman]] and Vincenzo C. A. Ferraro wrote an article, ''A New Theory of Magnetic Storms'', that sought to explain the phenomenon.<ref>{{cite journal|author1=S. Chapman|author2=V. C. A. Ferraro|date=1930|title=A New Theory of Magnetic Storms|journal=[[Nature (journal)|Nature]]|volume=129|issue=3169|pages=129–130|bibcode=1930Natur.126..129C|doi=10.1038/126129a0|s2cid=4102736}}</ref> They argued that whenever the [[Sun]] emits a [[solar flare]] it also emits a plasma cloud, now known as a [[coronal mass ejection]]. They postulated that this [[Plasma (physics)|plasma]] travels at a velocity such that it reaches Earth within 113 days, though we now know this journey takes 1 to 5 days. They wrote that the cloud then compresses the [[Earth's magnetic field]] and thus increases this field at the Earth's surface.<ref>{{cite journal|author=V. C. A. Ferraro|date=1933|title=A New Theory of Magnetic Storms: A Critical Survey|journal=[[The Observatory (journal)|The Observatory]]|volume=56|pages=253–259|bibcode=1933Obs....56..253F}}</ref> Chapman and Ferraro's work drew on that of, among others, [[Kristian Birkeland]], who had used recently-discovered [[cathode-ray tube]]s to show that the rays were deflected towards the [[Magnetic polarity|poles]] of a magnetic sphere. He theorised that a similar phenomenon was responsible for [[aurora]]s, explaining why they are more frequent in polar regions.