Editing Magnetometer (section)

===Auroras===
Magnetometers can give an indication of auroral activity before the [[light]] from the [[aurora]] becomes visible. A grid of magnetometers around the world constantly measures the effect of the solar wind on the Earth's magnetic field, which is then published on the [[K-index]].<ref>{{cite web |date=1 October 2007 |title=The K-index |publisher=[[Space Weather Prediction Center]] |url=http://www.swpc.noaa.gov/info/Kindex.html |access-date=2009-10-21 |url-status=dead |archive-url=https://web.archive.org/web/20131022183358/http://www.swpc.noaa.gov/info/Kindex.html |archive-date=22 October 2013 }}</ref>