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The Solar Cycle

The number of sunspots increases and decreases over time in a regular, approximately 11-year cycle, called the sunspot cycle. The exact length of the cycle can vary. It has been as short as eight years and as long as fourteen, but the number of sunspots always increases over time, and then returns to low again.

More sunspots mean increased solar activity, when great blooms of radiation known as solar flares or bursts of solar material known as coronal mass ejections (CMEs) shoot off the sun's surface. The highest number of sun spots in any given cycle is designated "solar maximum," while the lowest number is designated "solar minimum." Each cycle, varies dramatically in intensity, with some solar maxima being so low as to be almost indistinguishable from the preceding minimum.

Sunspots are a magnetic phenomenon and the entire sun is magnetized with a north and a south magnetic pole just like a bar magnet. The comparison to a simple bar magnet ends there, however, as the sun's interior is constantly on the move.

By tracking sound waves that course through the center of the sun, an area of research known as helioseismology, scientists can gain an understanding of what's deep inside the sun. They have found that the magnetic material inside the sun is constantly stretching, twisting, and crossing as it bubbles up to the surface. The exact pattern of movements is not conclusively mapped out, but over time they eventually lead to the poles reversing completely.

The sunspot cycle happens because of this poles flip -- north becomes south and south becomes north--approximately every 11 years. Some 11 years later, the poles reverse again back to where they started, making the full solar cycle actually a 22-year phenomenon. The sun behaves similarly over the course of each 11-year cycle no matter which pole is on top, however, so this shorter cycle tends to receive more attention.

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Other multimedia items related to this story:
     The Solar Dynamo: Toroidal and Poloidal Magnetic Fields (id 3521)
     Coronal Mass Ejections (CMEs) Blast Their Way Through the Solar System (id 10846)

Short, narrated video about the solar cycle.    Short, narrated video about the solar cycle.

For complete transcript, click here.
Duration: 3.4 minutes
Available formats:
  1280x720 (59.94 fps) QT         3 GB
  1280x720 (59.94 fps) QT         693 MB
  1280x720 (29.97 fps) QT         158 MB
  960x720 (29.97 fps) MPEG-4   122 MB
  1280x720 (30 fps) QT         99 MB
  1280x720 (29.97 fps) MPEG-4   61 MB
  1280x720 (59.94 fps) QT         49 MB
  640x360 (29.97 fps) MPEG-4   36 MB
  320x180 (29.97 fps) MPEG-4   15 MB
  1280x720   PNG           1 MB
  960x540 (29.97 fps) WEBM         47 MB
  320x180     PNG           269 KB
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Animation Number:10804
Animators:Scott Wiessinger (USRA)
 Walt Feimer (HTSI)
 Tom Bridgman (GST)
Video Editor:Scott Wiessinger (USRA)
Narrator:Karen Fox (ASI)
Producer:Scott Wiessinger (USRA)
Videographer:Rob Andreoli (AIMM)
Writers:Karen Fox (ASI)
 Scott Wiessinger (USRA)
Series:Narrated Movies
 Goddard Shorts
Goddard TV Tape:G2011-082 -- Solar Cycle
Please give credit for this item to:
NASA/Goddard Space Flight Center
SVS >> Coronal Mass Ejection
SVS >> Magnetic Fields
SVS >> Music
SVS >> Solar Cycle
SVS >> Solar Flare
SVS >> Sun
GCMD >> Earth Science >> Sun-earth Interactions
SVS >> Space Weather
SVS >> Edited Feature
SVS >> Heliophysics
DLESE >> Narrated
SVS >> Sunspot Cycle
SVS >> Sunspot
NASA Science >> Sun

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Many of our multimedia items use the GCMD keywords. These keywords can be found on the Internet with the following citation:
Olsen, L.M., G. Major, K. Shein, J. Scialdone, S. Ritz, T. Stevens, M. Morahan, A. Aleman, R. Vogel, S. Leicester, H. Weir, M. Meaux, S. Grebas, C.Solomon, M. Holland, T. Northcutt, R. A. Restrepo, R. Bilodeau, 2013. NASA/Global Change Master Directory (GCMD) Earth Science Keywords. Version logo - the U.S. Government's official Web portal. + Privacy Policy and Important Notices
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