Coronal mass ejection

A coronal mass ejection, on the left side of the image, captured at 9:25 p.m. Tuesday. This sun itself is obscured in this image, called a coronagraph, in order to better see the dimmer structures around it. (ESA/NASA Solar Heliospheric Observatory / March 13, 2013)

The sun has spewed a pair of solar particle blasts toward three NASA unmanned spacecraft in recent days -- including one on a University of Maryland-led mission.

But the risk of electronic malfunctioning is expected to be low and no impact on Earth is forecast, NASA said.

The coronal mass ejections occurred at 8:36 p.m. Tuesday and 6:54 a.m. Wednesday. The CMEs sent solar particles flying at about 400 miles per second, a rate that would have them reach Earth within a few days.

But at that speed, the particles are not expected to generate any noticeable impacts on Earth. A typical concern would be a geomagnetic storm that can disrupt satellite signals and GPS.

The CME could, however make for a brilliant aurora borealis, or "Northern Lights".

One of the spacecraft in the path of one of the CMEs is known as EPOXI, a mission the University of Maryland, College Park, is leading to explore faraway planets, comets and asteroids. The mission " combines two exciting science investigations in an entirely new mission that re-uses the Deep Impact spacecraft already in orbit around the Sun."

Deep Impact launched in 2004 and a year and a half later landed on the surface of comet Tempel 1.