Magnetic properties of orphan penumbrae

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A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
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Date

2025-09-01

Department

Department of Computer Science

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Mcode

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Language

en

Pages

11

Series

Astronomy & Astrophysics, Volume 701, pp. 1-11

Abstract

Orphan penumbrae (OPU) are features resembling sunspot penumbrae, but are not connected to an umbra. Here we compare OPUs and sunspot penumbrae, including their filaments. We also identify and describe the main mechanisms for the formation of OPUs and we characterise their decay process. Our study is based on spectropolarimetric inversions of active regions observed with the Hinode spectropolarimeter. We manually identified 80 individual OPUs, allowing us to study them statistically. In addition, we analysed the time evolution of selected OPUs using data provided by the Helioseismic and Magnetic Imager. Orphan penumbrae display a broad range of shapes, associated with typically Ω shaped magnetic field configurations, where opposite polarity fields predominate at the two ends of the OPU. In addition, the properties of the OPU filaments are remarkably uniform between different OPUs, resembling the ones in sunspot penumbrae. Most OPUs form by either a patch of a penumbra separating from a sunspot, or by new magnetic flux emerging close to the polarity inversion line of an active region. We observe chromospheric fibrils above almost all OPUs in Hinode Hα images, indicating that a part of the magnetic field of the OPUs extends to the chromosphere. Our results show that OPU filaments can form given a broad range of boundary conditions for the magnetic field.

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Publisher Copyright: © The Authors 2025.

Keywords

Sun: magnetic fields, Sun: photosphere

Other note

DOI

10.1051/0004-6361/202555610

Citation

Castellanos Durán, J S, Löptien, B, Korpi-Lagg, A, Solanki, S K & Van Noort, M 2025, 'Magnetic properties of orphan penumbrae', Astronomy & Astrophysics, vol. 701, A49, pp. 1-11. https://doi.org/10.1051/0004-6361/202555610

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https://urn.fi/URN:NBN:fi:aalto-202509237359

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[article-cris] Perustieteiden korkeakoulu / SCI