Superstrong photospheric magnetic fields in sunspot penumbrae

Abstract

Recently, there have been some reports of unusually strong photospheric magnetic fields (which can reach values of over 7 kG) inferred from Hinode SOT/SP sunspot observations within penumbral regions. These superstrong penumbral fields are even larger than the strongest umbral fields on record and appear to be associated with supersonic downflows. The finding of such fields has been controversial since they seem to show up only when spatially coupled inversions are performed. Here, we investigate and discuss the reliability of those findings by studying in detail observed spectra associated with particularly strong magnetic fields at the inner edge of the penumbra of active region 10930. We apply classical diagnostic methods and various inversions with different model atmospheres to the observed Stokes profiles in two selected pixels with superstrong magnetic fields, and compare the results with a magnetohydrodynamic simulation of a sunspot whose penumbra contains localized regions with strong fields (nearly 5 kG at $\tau =1$) associated with supersonic downflows...

arXiv comment19 pages, 14 figures, 3 tables. Now accepted for publication in Section 9. The Sun of Astronomy and Astrophysics. Date of acceptance is 23/09/2019

References in corpus (12)

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• Model selection for spectro-polarimetric inversions
• Evershed and counter-Evershed flows in sunspot MHD simulations

Cited by in corpus (8)

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• Formation of super-strong horizontal magnetic field in delta-type sunspot in radiation magnetohydrodynamic simulations
• How rare are counter Evershed flows?
• Expulsion of counter Evershed flows from sunspot penumbrae
• The MODEST catalog of depth-dependent spatially coupled inversions of sunspots observed by Hinode/SOT-SP
• Three-dimensional simulations of accretion flow in the progenitor of Tycho's supernova
• Superstrong magnetic fields in sunspot bipolar light bridges