On June 20, 2013, at 11:24 p.m., the sun erupted with an Earth-directed coronal（冠状的） mass ejection or CME, a solar phenomenon that can send billions of tons of particles into space that can reach Earth one to three days later. These particles cannot travel through the atmosphere to harm humans on Earth, but they can affect electronic systems in satellites and on the ground. Experimental NASA research models, based on observations from NASA's Solar Terrestrial Relations Observatory¹ and ESA/NASA's Solar and Heliospheric Observatory show that the CME left the sun at speeds of around 1350 miles per second, which is a fast speed for CMEs.

 

Earth-directed CMEs can cause a space weather phenomenon called a geomagnetic（地磁的） storm, which occurs when they funnel² energy into Earth's magnetic envelope, the magnetosphere, for an extended period of time. The CME's magnetic fields peel back the outermost³ layers of Earth's fields changing their very shape. Magnetic storms can degrade communication signals and cause unexpected electrical surges in power grids⁴. They also can cause aurora⁵. Storms are rare during solar minimum, but as the sun's activity ramps⁶ up every 11 years toward solar maximum -- currently expected in late 2013 -- large storms occur several times per year.

 

In the past, geomagnetic storms caused by CMEs of this strength and direction have usually been mild.

 

In addition, the CME may pass by additional spacecraft: Messenger, STEREO B, Spitzer, and their mission operators have been notified. If warranted, operators can put spacecraft into safe mode to protect the instruments from the solar material.

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