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    What Exactly Is a X-Class Solar Flare?

    By travel
    8/10/2011, 5:22:47 AM

    We have heard recently about how busy the Sun is and how events like solar flares, sunspots and coronal mass ejections (CMEs) have been occurring with regular frequency. I figured now would be a great time to talk about a X-class solar flares.

    Solar flares are giant explosions on the Sun that send energy, light and high speed particles into space. These flares are often associated with CMEs. The number of solar flares increases approximately every 11 years, and the Sun is currently moving towards another solar maximum, likely in 2013. That means more flares will be coming, some small and some big enough to send their radiation all the way to Earth.

    The biggest flares are known as “X-class flares” based on a classification system that divides solar flares according to their strength. The smallest ones are A-class (near background levels), followed by B, C, M and X. Similar to the Richter scale for earthquakes, each letter represents a 10-fold increase in energy output. So an X is 10 times an M and 100 times a C. Within each letter class there is a finer scale from 1 to 9.

    C-class and smaller flares are too weak to affect Earth noticeably. M-class flares can cause brief radio blackouts at the poles and minor radiation storms that might endanger astronauts.

    Then come the X-class flares. Although X is the last letter, there are flares more than 10 times the power of an X1, so X-class flares can go higher than 9. The most powerful flare measured with modern methods was in 2003, during the last solar maximum, and it was so powerful that it overloaded the sensors measuring it. The sensors cut out at X28.

    The biggest X-class flares are, by far, the largest explosions in the solar system and are awesome to watch. Loops tens of times the size of Earth leap up off the Sun’s surface when the Sun’s magnetic fields cross over each other and reconnect. In the biggest events, this reconnection process can produce as much energy as a billion hydrogen bombs.

    If they’re directed at Earth, such flares and associated CMEs can create long lasting radiation storms that can harm satellites, communications systems and even ground-based technologies and power grids. X-class flares on Dec. 5 and 6, 2006, for example, triggered a CME that interfered with GPS signals being sent to ground-based receivers.

    NASA, NOAA, the US Air Force Weather Agency (AFWA) and others keep a constant watch on the Sun to monitor for X-class flares and their associated magnetic storms. With advance warning, many satellites and spacecraft can be protected from the worst effects.


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    Astronomy blog