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Last Post 10/21/2013 11:06 AM by  KD Leka
sunspot size
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10/20/2013 8:59 PM
    Liz A What determine's the size of a sunspot, and how big is the biggest ever seen?
    Tags: sunspots

    Lindsay Glesener

    New Member

    New Member

    10/21/2013 10:49 AM
    Sunspots are places where the magnetic field beneath the solar surface (the photosphere) "punctures" the surface and continues into the outer solar atmosphere (the corona). So the size of the sunspot depends on the magnetic field: If the magnetic field is strong but concentrated, the sunspot could be quite small. If the magnetic field is more spread out, the sunspot will be larger.

    Many sunspots are as big as the Earth's area, and large ones can be 10 times or even up to almost 50 times as large as the Earth. I'm not sure which one is the largest so far, but this website has some interesting information about some notably large sunspots:

    And sunspots are grouped together in "active regions," which are regions that have very complicated magnetic fields. These sunspot groups are the places where most solar flares come from!

    KD Leka

    Basic Member

    Basic Member

    10/21/2013 11:06 AM

    Howdy, Liz;

    Indeed, it's essentially how much total magnetic flux -- field strength times area -- that gathers together to make a sunspot bigger. And, although I do hate to sound like an old geezer, this solar cycle maximum that we're in now has been notable in the lack of really big sunspots. Still, if you can look at the images of today's Solar disk (see, e.g.,, which is a very nice site...), there's a fairly respectable-sized sunspot rotating into view. Take a look on the website. If you have binoculars or similar, and use the projection method (do NOT look directly at the Sun or look through binoculars at the Sun!!!), this big sunspot will be easily visible.

    have fun, -KD

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