May 1921 geomagnetic storm

An exceptionally powerful geomagnetic storm that struck the Earth from 13-15 May 1921

The three-day May 1921 geomagnetic storm, also known as the New York Railroad Storm, was caused by the impact of an extraordinarily powerful coronal mass ejection on Earth's magnetosphere. It occurred on 13–15 May as part of solar cycle 15, and was the most intense geomagnetic storm of the 20th century.

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