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A CME, one type of "solar storm", erupts from the Sun in January 2002. The actual disc of the Sun, indicated by the white circle, is hidden in this view through an instrument called a coronagraph. The coronagraph creates an artificial eclipse by blocking the too-bright light from the Sun's surface, allowing us to view the Sun's dimmer atmosphere.
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Images courtesy SOHO (NASA & ESA). Animation by Windows to the Universe staff (Randy Russell).

Solar Storms

You know, of course, that certain conditions in the Earth's atmosphere can cause powerful storms like thunderstorms, blizzards, tornadoes, and hurricanes. The Sun also has an atmosphere, and incredible storms that dwarf Earthly storms sometimes blast forth from the Sun's surface into the solar atmosphere.

The two main types of storms on the Sun are solar flares and Coronal Mass Ejections (CMEs). Both storms have to do with tangled magnetic fields in the neighborhood of active regions on the Sun's surface. Like a rubber band that is twisted until it snaps, the tangled magnetic fields around an active region release energy when they "snap". The energy given off in a matter of minutes by a solar flare can be as much as is given off by 100 hurricanes on Earth!

Solar flares emit energy in the form of electromagnetic radiation, including X-rays, ultraviolet radiation, visible light, and radio waves. A solar flare typically lasts a few minutes to as long as an hour.

CMEs are explosions in the corona, the top part of the Sun's atmosphere. These explosions throw out a huge bubble of billions of tons of gas and plasma into space. A CME typically releases about the same amount of energy as a flare, but it lasts several hours instead of minutes. If the CME is "aimed" at Earth, it takes about one to four days to reach us from the Sun.

The energy from solar storms can be dangerous if it reaches Earth! Astronauts on spacewalks are in danger of increased radiation exposure, and electronics on satellites can be fried. Earth's magnetic field and atmosphere shield those of us on the ground from most of the dangerous radiation thrown out by solar storms.

Sometimes, if we're lucky, solar storms can offer us a wonderful (safe!) treat. The beautiful displays of the aurora (Northern and Southern Lights) are results of solar storms.

Some "seasons" are stormier than others on the Sun. Sunspots are more common during "storm seasons" on the Sun. The number of sunspots rises and falls in an 11-year cycle, and an increase in the sunspot count means an increase in solar activity or solar storms will follow.

Last modified January 12, 2010 by Randy Russell.

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF