geomagnetic storm


Origin:
1940–45

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Main Entry:  geomagnetic storm
Part of Speech:  n
Definition:  a worldwide disturbance of the earth's magnetic field induced by solar flares, solar wind, or sunspot activity; also called [magnetic storm]
Etymology:  1836-41
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Encyclopedia Britannica
Encyclopedia

geomagnetic storm

disturbance of the Earth's upper atmosphere brought on by solar flares-i.e., bright eruptions from the visible portion of the Sun's chromosphere. The material associated with these flares consists primarily of protons and electrons with an energy of a few thousand electron volts. Called plasma, this material moves through the interplanetary medium at speeds ranging from 1,000 to 2,000 km (600 to 1,200 miles) per second, so that the ejected material reaches the Earth in approximately 21 hours. The pressure of the incoming plasma is transmitted to the outer edge of the Earth's magnetosphere; this causes an increase in the observed geomagnetic field at the ground, perhaps through hydromagnetic waves

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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