Spectropolarimetric fluctuations in a sunspot chromosphere

Marco Stangalini, D. Baker, G. Valori, D. B. Jess, S. Jafarzadeh, M. Murabito, A. S.H. To, D. H. Brooks, I. Ermolli, F. Giorgi, C. D. MacBride

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The instrumental advances made in this new era of 4 m class solar telescopes with unmatched spectropolarimetric accuracy and sensitivity will enable the study of chromospheric magnetic fields and their dynamics with unprecedented detail. In this regard, spectropolarimetric diagnostics can provide invaluable insight into magneto-hydrodynamic (MHD) wave processes. MHD waves and, in particular, Alfvénic fluctuations associated with particular wave modes were recently recognized as important mechanisms not only for the heating of the outer layers of the Sun's atmosphere and the acceleration of the solar wind, but also for the elemental abundance anomaly observed in the corona of the Sun and other Sun-like stars (also known as first ionization potential) effect. Here, we take advantage of state-of-the-art and unique spectropolarimetric Interferometric BIdimensional Spectrometer observations to investigate the relation between intensity and circular polarization (CP) fluctuations in a sunspot chromosphere. Our results show a clear link between the intensity and CP fluctuations in a patch which corresponds to a narrow range of magnetic field inclinations. This suggests the presence of Alfvénic perturbations in the sunspot. This article is part of the Theo Murphy meeting issue 'High-resolution wave dynamics in the lower solar atmosphere'.

Original languageEnglish
Article number20200216
Number of pages14
JournalPhilosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
Issue number2190
Early online date21 Dec 2020
Publication statusPublished - 08 Feb 2021

Bibliographical note

Funding Information:
Data accessibility. The IBIS data that support the plots within this paper and other findings of this study can be downloaded from the IBIS-A archive http://ibis.oa-roma.inaf.it/IBISA/database/. Authors’ contributions. M.S. carried out the experiments and conceived of and designed the study. M.S. performed the data reduction and scientific analysis, with assistance from D.B., G.V., D.B.J., S.J., M.M., A.S.H.T., D.H.B., I.E., F.G. and C.D.M. M.S. drafted the manuscript with the help of D.B., G.V., D.J. and S.J. All authors read and approved the manuscript. Competing interests. We declare we have no competing interests. Funding. This work was supported by An Invest NI and Randox Laboratories Ltd Research & Development grant no. (059RDEN-1); European Research Council (grant agreement no. 682462); Research Council of Norway (project no. 262622); The Department for the Economy (Northern Ireland) through their postgraduate research studentship; European Union’s Horizon 2020 Research and Innovation programme under grant agreement no. 82135 (SOLARNET) and no. 739500 (PRE-EST) Acknowledgements. The authors wish to acknowledge scientific discussions with the Waves in the Lower Solar Atmosphere (WaLSA; www.WaLSA.team) team, which is supported by the Research Council of Norway (project number 262622), and The Royal Society through the award of funding to host the Theo Murphy Discussion Meeting ‘High-resolution wave dynamics in the lower solar atmosphere’ (grant Hooke18b/SCTM). D.B.J. is grateful to Invest NI and Randox Laboratories Ltd for the award of a Research & Development grant no. (059RDEN-1). S.J. acknowledges support from the European Research Council under the European Unions Horizon 2020 research and innovation programme (grant agreement no. 682462) and from the Research Council of Norway through sits Centres of Excellence scheme (project No. 262622). C.D.M. thanks the Northern Ireland Department for the Economy for the award of a PhD studentship. D.B. is funded under STFC consolidated grant no. ST/S000240/1. This research has received funding from the European Union’s Horizon 2020 Research and Innovation programme under grant agreement no. 824135 (SOLARNET), the STFC grant nos ST/T000317/1 and 739500 (PRE-EST). This research has made use of the IBIS-A archive.

Publisher Copyright:
© 2020 The Author(s).

Copyright 2021 Elsevier B.V., All rights reserved.


  • chromospheric dynamics
  • solar MHD waves
  • solar spectropolarimetry

ASJC Scopus subject areas

  • General Mathematics
  • General Engineering
  • General Physics and Astronomy


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