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AURORA ALERT: An interplanetary shock wave struck Earth's magnetosphere early on Friday the 13th and triggered a strong geomagnetic storm. Forecasters anticipate that a second shock wave will arrive later Friday or Saturday, possibly intensifying the ongoing disturbance. Middle-latitude sky watchers should remain alert for auroras after local sunset.

AURORA GALLERY: A pair of coronal mass ejections that hit Earth's magnetosphere on April 11th sparked an intense display of auroras. Sky watchers in the United States saw "Northern Lights" as far south as the New Mexico-Texas border. Check out our aurora gallery for more than 50 images of the storm.

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