A Coronal Mass Ejection (CME) earlier in the week has sent a burst of energy from the sun and a stream of particles to our planet. Normal amounts are usually deflected around Earth by a doughnut shaped magnetic shield around Earth, but increased levels from solar storms like this find their way into that doughnut hole. Enough energy and the line where the aurora is visible extends further south.
Normally something visible only in parts of Alaska and northern Canada, that line is forecasted to extend into the northern US from NYC westward to northern Oregon Wednesday night into Friday morning. Some auroral activity (expect a greening of the sky, not the beautiful ribbons on light you may have seen in photos) as far south as North Carolina west to Northern California.
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