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Last Post 23 Oct 2018 08:57 PM by  KD Leka
Magnetic field
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John E.
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21 Oct 2018 11:13 PM
    What is the strength of a magnetic field in a sunspot?
    >100 Answers
    Posts:151 >100 Answers

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    22 Oct 2018 06:54 AM
    The strength of the magnetic field within a sunspot ranges from 1,000 to 4,000 Gauss
    >50 Answers
    Posts:73 >50 Answers

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    23 Oct 2018 02:53 PM
    John E. the strength of a refrigerator magnet can be about 50 Gauss and the strength of Earth's magnetic field is about 0.5 Gauss.
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    Posts:105 >100 Answers

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    23 Oct 2018 08:57 PM
    Hi John;
    I'm going to elaborate a little on Dawn's answer, with just a little bit of, "we don't really know". We do know it to about that level of accuracy, and we know that certain parts of sunspots have stronger fields than other parts, point in different directions, etc.

    However, solar physics is (generally speaking) a "remote-sensing science", which means that in all honesty, "all we have are photons". Except for sampling the solar wind and the similar neat stuff that Parker Solar Probe will do, we do not get to stick a magnetic probe into a sunspot and measure the field strength directly. All we have to measure are photons that pass through the fields, and the impact that the magnetic fields have on light and plasma, and we kind of "work backwards" to say "what is the field strength that would cause the effect I see?" For example, we use the Zeeman effect by which photons that are passing in the vicinity of strong magnetic fields get polarized, and their energies get impacted slightly, so that for a "magnetically sensitive spectral line" (not all parts of the spectrum are sensitive), we can detect those changes and infer the magnetic field strengths from them. We have developed many many tools in this field of "solar spectro-polarimetry" and "solar magnetetography", but it is still an active area of research, especially as larger and more sensitive instruments are built and we can measure these indirect effects better and at higher spatial and temporal resolution (the latter being really important because of the really dynamic nature of the thing we are trying to investigate).

    A couple of links:
    https://www.cfa.harvard.edu/~lwools...Effect.pdf
    https://www2.hao.ucar.edu/Education...e-sunspots
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