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Last Post 10/23/2018 7:20 PM by  KD Leka
depth of sunspots
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Author Messages

Zach M


10/21/2018 10:11 PM
    how deep do sunspots go?

    Paulett Liewer

    Basic Member

    Basic Member

    10/22/2018 10:14 AM
    Sunspots -- the dark spots visible on the solar surface -- appear dark only because they are not quite as hot as the surrounding surface (called the photosphere). Sunspots are about 3000-4000 degrees C whereas the rest of the photosphere is about 5500 degrees C. The regions themselves are slight depression of the surface and associated flows are thought to be rather shallow. Sunspots are the visible manifestation of magnetic flux tubes that probably have risen to the surface through the Sun's convection zone which extends to about a third of the way to the core of the Sun. Scientist really don't yet understand how these flux tubes are created. The convection zone is a very very turbulent plasma (ionized gas) where the heat from the core, generated there by fusion, is convected up to the surface. The Sun is really an amazingly complex object..and we are still trying to understand it.

    By the way, other stars have spots, too!

    KD Leka

    Basic Member

    Basic Member

    10/23/2018 7:20 PM
    Hi - just to add to what Paulette wrote, the reason that the sunspots are darker (cooler) is due to the intense magnetic fields there. And to echo what Paulette said - questions about how those magnetic fields are created in the solar interior, sustained during their rise from the interior to the surface and upper atmosphere, condensed to form such concentrated regions -- are all active research.

    But a few fun tidbits:
    (1) depending on "how" you look (using what part of the electromagnetic spectrum), sunspots may look dark (such as when you see them in visible light) or bright (as when you look at them in radio).
    (2) Generally speaking, it's safe to say they're kinda flat. A small-medium sized sunspot will extend 10--20 x 10^6m wide(we short-hand that as 10-20 mega-meters). But the dip that we kinda see in the middle, and the height that those penumbral fibrals extent (in the visible-light photosphere) are all maybe 0.1 -- 0.5 Mm in height, so that's a 20:1 ratio. (For perspective,
    the diameter of the Earth is about 12Mm.)

    (3) With helioseismology (the study of the sound waves traveling through the sun) we can actually see under sunspots -- and they do influence the sun underneath them to a depth of many 10s of Mm. We can't see underneath them very well, so it's still a bit of a puzzle exactly what the magnetic field and the plasma is really doing under there. But something is happening....
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