A temporary, significant disturbance of Earth's magnetic field caused by an especially strong burst of solar wind or a coronal mass ejection from the sun striking the planet's magnetosphere. Severe geomagnetic storms can disrupt satellite operations, radio communications and electrical power grids, and are the direct driver of unusually widespread and vivid auroral displays, occasionally pushing the aurora to latitudes far from its normal range.
Facts
PeriodicityFrequency rises and falls with the roughly eleven-year sunspot cycle, occurring more often during solar maxima, when most are driven by coronal mass ejections. 1 ScaleRated on the NOAA G-scale from G1, the weakest (Kp value of 5), to G5, the strongest (Kp value of 9). 1 First DescribedThe first scientific observation of a geomagnetic storm's effects came in the early nineteenth century, when Alexander von Humboldt, recording a compass bearing in Berlin from 1806 to 1807, noticed on 21 December 1806 that his compass had become erratic during a bright auroral event; a physical theory of the phenomenon followed in 1930, when Sydney Chapman and Vincenzo Ferraro proposed that a solar plasma cloud, now called a coronal mass ejection, was the cause. 1 Identification
Distinguishing AppearanceA temporary disturbance of Earth's magnetosphere driven by solar plasma and magnetic structures such as coronal mass ejections; the visible signature at the ground is an intensified aurora that can extend to unusually low latitudes, alongside a disturbed compass needle. 1 Connections
Associated With
A geomagnetic storm intensifies and expands auroral activity toward lower latitudes by injecting additional charged particles into the upper atmosphere along magnetic field lines.
A sufficiently powerful solar flare, especially one paired with a coronal mass ejection, is a direct and well-established trigger of a geomagnetic storm when the ejected material reaches Earth's magnetosphere.
Sources
1. Geomagnetic Storm (Wikipedia)
WikipediaWikipedia 'Geomagnetic storm', lead section
A geomagnetic storm, also known as a magnetic storm, is a temporary disturbance of the Earth's magnetosphere that is driven by interactions between the magnetosphere and large-scale transient plasma and magnetic field structures that originate on or near the Sun.
Wikipedia 'Geomagnetic storm', History and Occurrences sections
The first scientific observation of the effects of a geomagnetic storm occurred early in the 19th century: from May 1806 until June 1807, Alexander von Humboldt recorded the bearing of a magnetic compass in Berlin.
Wikipedia 'Geomagnetic storm', lead section (periodicity sentence)
The frequency of geomagnetic storms increases and decreases with the sunspot cycle. During solar maxima, geomagnetic storms occur more often, with the majority driven by CMEs.
Wikipedia 'Geomagnetic storm', lead section (scale sentence)
where G1 is the weakest storm classification (corresponding to a Kp value of 5), and G5 is the strongest (corresponding to a Kp value of 9)
Wikipedia 'Geomagnetic storm', lead section (distinguishing-appearance sentence)
A geomagnetic storm, also known as a magnetic storm, is a temporary disturbance of the Earth's magnetosphere that is driven by interactions between the magnetosphere and large-scale transient plasma and magnetic field structures that originate on or near the Sun.
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