UPDATE: The M9.4 flare on Oct. 23, 2013, was associated with a coronal mass ejections 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.

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To see how this event may impact Earth, please visit NOAA's Space Weather Prediction Center at http://spaceweather.gov, the U.S. government's official source for space weather forecasts, alerts, watches and warnings.

CMEs can cause a spaceweather phenomenon called a geomagnetic storm, which occurs when they connect with the outside of Earth's magnetic envelope, the magnetosphere, for an extended period of time. In the past, geomagnetic storms caused by CMEs of this strength have usually been mild.

NASA's SDO Sees Sun Emit a Mid-level Solar Flare - Oct. 24, 2013

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The sun emitted a mid-level solar flare that peaked at 8:30 pm EDT on Oct. 23, 2013. Solar flares are powerful bursts of radiation. Harmful radiation from a flare cannot pass through Earth's atmosphere to physically affect humans on the ground, however -- when intense enough -- they can disturb the atmosphere in the layer where GPS and communications signals travel. Such radiation can disrupt radio signals for as long as the flare is ongoing, anywhere from minutes to hours.

To see how this event may impact Earth, please visit NOAA's Space Weather Prediction Center at http://spaceweather.gov, the U.S. government's official source for space weather forecasts, alerts, watches and warnings.

This flare is classified as an M9.4 flare, on a scale from M1 to M9.9. This rating puts it at the very top of the scale for M class flares, which are the weakest flares that can cause some space weather effects near Earth. In the past, they have caused brief radio blackouts at the poles. The next highest level is X-class, which denotes the most intense flares.

Increased numbers of flares are quite common at the moment, since the sun is near solar maximum. Humans have tracked solar cycles continuously since they were discovered in 1843, and it is normal for there to be many flares a day during the sun's peak activity.

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