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Last Post 29 Mar 2017 01:01 PM by  Terry Kucera
sun
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henry l





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29 Mar 2017 08:09 AM
    Do the temperatures at the sun's poles differ much from other regions on its surface?
    Tags: temperature, Sun, surface, poles


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    29 Mar 2017 01:01 PM
    Hi Henry,
    The sun's poles are hot, but solar poles are very interesting places - not just like everywhere else on the sun.

    As you probably know, know Earth's poles are cooler because of the effects of the seasons and the angle of the sun's light hitting them. These are not factors in the sun's temperature because the sun heats itself.

    But the Sun is not the same everywhere. When we look at the sun's atmosphere, the corona, in X-ray or ultraviolet light we see that the poles are generally covered by dark regions that we call "coronal holes".
    Here is a picture of the Sun taken today in high energy ultraviolet light by the SDO spacecraft:
    http://sdowww.lmsal.com/sdomedia/SunInTime/2017/03/29/l0211.jpg

    The north pole is pointed away from us a bit, but you can clearly see a big dark area to the south. This is the "hole". All of the Sun's corona is quite hot, a million degrees Celsius or more and that hot material glows in the UV and X-rays. The "holes," however, are dark because there is less of that hot material there. This is because the magnetic fields from these areas open up into the solar system, so that hot atmosphere can escape the sun easily, while in other parts of the Sun the magnetic field keeps it bottled up near the surface.

    These coronal holes are, as I said, usually seen near the Sun's poles, but sometimes they show up in other areas of the Sun too - all part of the Sun's complex, changing magnetic field. That magnetic field and the resulting solar activity are what make the Sun so interesting.

    Terry
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