On Jan. 23, 2013, at 9:55 a.m. EST, the sun erupted with an Earth-directed coronal mass ejection, or CME. Experimental NASA research models, based on observations from the Solar Terrestrial Relations Observatory (STEREO) and ESA/NASA's Solar and Heliospheric Observatory, show that the CME left the sun at speeds of around 375 miles per second, which is a fairly typical speed for CMEs.
Not to be confused with a solar flare, a CME is a solar phenomenon that can send solar particles into space and reach Earth one to three days later.
Earth-directed CMEs can cause a space weather phenomenon called a geomagnetic storm, which occurs when they connect with the outside of the Earth's magnetic envelope, the magnetosphere, for an extended period of time. In the past, CMEs of this speed have not caused substantial geomagnetic storms. They sometimes cause auroras near the poles but are unlikely to affect electrical systems on Earth or interfere with GPS or satellite-based communications systems.
A slightly slower CME that was not Earth-directed, also erupted earlier in the day.
NOAA's Space Weather Prediction Center is the United States government's official source for space weather forecasts.
Updates will be provided if needed.
What is a CME?
For answers to this and other space weather questions, please visit the Spaceweather Frequently Asked Questions page: http://www.nasa.gov/mission_pages/sunearth/spaceweather/index.html