Auroras possible farther south as CMEs reach Earth, NOAA issues watch

Multiple coronal mass ejections launched from the Sun between October 11 and 13 are expected to reach Earth on October 16, prompting the U.S. National Oceanic and Atmospheric Administration's Space Weather Prediction Center to issue a geomagnetic storm watch that could make the Northern Lights visible much farther south than usual. Forecasters say the most likely period for enhanced auroral activity runs from Thursday evening into early Friday, with the greatest chances for displays late Thursday night and into the following morning, though timing remains approximate.

Coronal mass ejections, or CMEs, are large eruptions of plasma and magnetic field from the Sun that can drive geomagnetic storms when they interact with Earth's magnetosphere. Space weather agencies say several CMEs, some associated with flaring from a large, magnetically complex sunspot region, are arriving in quick succession. NOAA's three day outlook places storm strength at minor to moderate, rated G1 to G2 on a five point scale, and indicates the Kp index, a global measure of geomagnetic activity, may reach about 5 or 6. Forecasters note the orientation of the interplanetary magnetic field, particularly the...