ANCHORAGE, Alaska (Sept. 18) - A huge sunspot has been blasting Earth with magnetic clouds for weeks, producing some of the most vibrant and visible summertime auroras in years, according to NASA scientists.

Dazzling Solar Light Show


Greg A. Syverson, Getty Images
A full moon helps illuminate the Alaskan oil pipeline under the glow of the Aurora Borealis near Milne Point.

Scientists say the magnetic flare-ups from Sunspot 798 will last at least through Friday.

"It is a fairly large geomagnetic storm that we've had over the past 24 hours, and it should continue a little while longer," said aurora researcher Dirk Lummerzheim, at the Geophysical Institute at the University of Alaska Fairbanks.

Skywide northern lights have awed Alaskans since last week and produced red displays as far south as Arizona.