A distinct magnetic property of the inner penumbral boundary
- J. Jurčák
- N. Bello González
- R. Schlichenmaier
- R. Rezaei
DOIAbstract
Context. We recently presented evidence that stable umbra-penumbra boundaries are characterised by a distinct canonical value of the vertical component of the magnetic field, Bstablever. In order to trigger the formation of a penumbra, large inclinations in the magnetic field are necessary. In sunspots, the penumbra develops and establishes by colonising both umbral areas and granulation, that is, penumbral magneto-convection takes over in umbral regions with Bver<Bstablever, as well as in granular convective areas. Eventually, a stable umbra-penumbra boundary settles at Bstablever. Aims. Here, we aim to study the development of a penumbra initiated at the boundary of a pore, where the penumbra colonises the entire pore ultimately. ...
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