Abstract
From an investigation of spectra in a magnetically sensitive (λ 6173, g = 2.5) and insensitive line (λ 5576, g = 0), we derived the following properties for a symmetrical sunspot:
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(a)
The magnetic field strength varies with the distance ρ(ρ ⩽ 1) from the sunspot center like H(ρ) = H(0) (1 + ρ 2)-1
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(b)
The zenith angle of the magnetic field varies like 90°ρ. From this and from H(ρ) we find a height gradient of 0.5 gs/km at ρ = 0.
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(c)
The equivalent width and the half width of λ 5576 show an increase in penumbral regions of maximum Evershed flow. Most likely this is due to a combination of inhomogeneities in the Evershed flow and ‘microturbulence’.
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(d)
We find the magnetic field strength to be larger in the dark interfilamentary regions of the penumbra. These regions move downwards with respect to the bright filaments and probably have a more horizontal magnetic field.
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(e)
In a weak light bridge and in extensions of bright penumbral filaments into the umbra, we find a decrease of the magnetic field strength, and a more horizontal field direction with respect to the umbral surrounding. li(f)
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Beckers, J.M., Schröter, E.H. The intensity, velocity and magnetic structure of a sunspot region. Sol Phys 10, 384–403 (1969). https://doi.org/10.1007/BF00145526
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DOI: https://doi.org/10.1007/BF00145526