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What Causes Aurora?

Will you be seeing an aurora tonight? Yesterday, January 23, 2012, an M8.7-class flare erupted from the Sun and sent a huge wave of high-energy protons towards Earth and Mars, moving at about 8 million kilometers per hour. According to Spaceweather.com, the CME hit Earth’s magnetic field at approximately 1500 UT (10 am EST) today, and geomagnetic storms are likely in the hours ahead, as scientists say this the largest solar storm Earth has encountered since 2005.

But what is an aurora and what causes them?

Aurora are colorful lights in the night sky and primarily appear in Earth’s polar regions. But what causes these colorful lights? (See a gallery of aurorae from January 22-23). When solar plasma is ejected from the Sun during a magnetic event like a flare or a coronal mass ejection, the plasma travels outward along with the solar wind and when it encounters Earth’s magnetic field, it travels down the field lines that connect at the poles. Atoms in the plasma interacts with atoms in Earth’s upper atmosphere, creating colorful dancing lights. Currently, with all the solar activity, lower than normal latitudes may see aurora.

Possible effects from the solar storm besides aurorae are power outages (geomagnetic storms can create electrical currents of hundreds of amps in long conductors on the ground, such as power transmission lines) and satellite damage, but both are very unlikely from this solar storm, which is not as powerful as the rather famous “Halloween Storms of 2003,” where the Solar and Heliospheric Observatory (SOHO) satellite failed temporarily and NASA’s Advanced Composition Explorer (ACE) satellite experienced damage, and instruments aboard many spacecraft had to be shut down temporarily.

In A 1994 solar storm caused major malfunctions to two communications satellites, disrupting newspaper, network television and nationwide radio service throughout Canada. Other storms have affected systems ranging from cell phone service and TV signals to GPS systems and electrical power grids. In March 1989, a solar storm caused the Hydro-Quebec (Canada) power grid to go down for over nine hours, and the resulting damages and loss in revenue were estimated to be in the hundreds of millions of dollars.

Here’s a look at yesterday’s activity from three different spacecraft:


Nancy Atkinson is Universe Today's Senior Editor. She also works with Astronomy Cast, and is a NASA/JPL Solar System Ambassador.

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