STRONG GEOMAGNETIC STORM: A fast-moving stream of solar wind hit Earth on Sept. 14th, sparking an unexpectedly strong G3-class geomagnetic storm. Overnight (Sept. 14-15), auroras appeared in the USA as far south as Colorado. The storm is subsiding now, but it's not over. Minor (G1) to moderate (G2) storms are possible throughout Sept. 15th.