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Solar Magnetic Flux Tubes

Solar Magnetic Flux Tubes (MFT), also called "pores", are magnetic field concentrations near the surface of the sun. They are caused by surrounding convective motion which brings together small components of magnetic field. There are three stages in the life of an MFT:

  1. Formation, which takes from three to five minutes
  2. Stable stage, which lasts tens of minutes
  3. Collapse, or the move to an unstable state, which again takes tens of minutes

Magnetic Flux Tubes & Sun Spots

Magnetic Flux Tubes are of interest because of their close relation to their much larger cousins: Sun Spots. By modeling MFT's it is hoped that more can be learned about Sun Spots.

Sun Spots are much larger and longer lived. They are the single biggest influence on the amount of solar radiation that reaches the earth, and can have tremendous impact on radio communications, and the thickness of the earth's atmosphere.

When sun spots are active they cause heating in the upper atmosphere, which in turn causes expansion. Skylab fell to earth prematurely in 1979 due to this phenomenon when an unexpected Sun Spot flared up. The launch of the Hubble telescope was delayed for a year because of Sun Spot activity.


Top View

QuickTime | Real | MPEG


Bottom View

QuickTime | Real | MPEG


The variable that is depicted in these visualizations is magnetic pressure. Magnetic pressure is defined as the strength of the magnetic field, squared. Brighter colors represent higher pressure. There is an inverse relationship between gas pressure and magnetic pressure. i.e. the brown regions are areas of high gas pressure.

The collapse of a Solar Magnetic Flux Tube (MFT) visualized in these animations is brought on due to cooling at the sun's surface. At the beginning of the animation you are seeing the ends of the stable stage. The pore in front, center is beginning to go unstable, as indicated by the formation of the two lobes in the blue areas. As the evolution progresses these twin lobes, which are characteristic of the unstable stage, become more and more distinct. The lobes are caused by the existence of a high-pressure gas regions which forms between the lobes.

John Clyne, NCAR/VETS
Peter Fox, NCAR/HAO
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