Volume 656, December 2021
|Number of page(s)||9|
|Section||The Sun and the Heliosphere|
|Published online||07 December 2021|
Investigating the origin of magnetic perturbations associated with the FIP Effect⋆
INAF Istituto Nazionale di Astrofisica, Osservatorio Astronomico di Roma, 00078 Monte Porzio Catone, RM, Italy
2 ASI – Agenzia Spaziale Italiana, Via del Politecnico snc, Rome, Italy
3 University College London, Mullard Space Science Laboratory, Holmbury St. Mary, Dorking, Surrey, RH5 6NT UK
4 Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
5 Astrophysics Research Centre, School of Mathematics and Physics, Queen’s University Belfast, Belfast, BT7 1NN UK
6 Department of Physics and Astronomy, California State University Northridge, Northridge, CA, 91330 USA
7 Rosseland Centre for Solar Physics, University of Oslo, PO Box 1029 Blindern 0315 Oslo, Norway
8 Institute of Theoretical Astrophysics, University of Oslo, PO Box 1029 Blindern 0315 Oslo, Norway
9 College of Science, George Mason University, 4400 University Drive, Fairfax, VA, 22030 USA
10 LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Univ. Paris Diderot, Sorbonne Paris Cité, 5 place Jules Janssen, 92195 Meudon, France
11 Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Konkoly Thege út 15-17., 1121 Budapest, Hungary
Accepted: 17 August 2021
Recently, magnetic oscillations were detected in the chromosphere of a large sunspot and found to be linked to the coronal locations where a first ionization potential (FIP) effect was observed. In an attempt to shed light on the possible excitation mechanisms of these localized waves, we further investigate the same data by focusing on the relation between the spatial distribution of the magnetic wave power and the overall field geometry and plasma parameters obtained from multi-height spectropolarimetric non-local thermodynamic equilibrium (NLTE) inversions of IBIS data. We find, in correspondence with the locations where the magnetic wave energy is observed at chromospheric heights, that the magnetic fields have smaller scale heights, meaning faster expansions of the field lines, which ultimately results in stronger vertical density stratification and wave steepening. In addition, the acoustic spectrum of the oscillations at the locations where magnetic perturbations are observed is broader than that observed at other locations, which suggests an additional forcing driver to the p-modes. Analysis of the photospheric oscillations in the sunspot surroundings also reveals a broader spectrum between the two opposite polarities of the active region (the leading spot and the trailing opposite polarity plage), and on the same side where magnetic perturbations are observed in the umbra. We suggest that strong photospheric perturbations between the two polarities are responsible for this broader spectrum of oscillations, with respect to the p-mode spectrum, resulting in locally excited acoustic waves that, after crossing the equipartition layer, located close to the umbra-penumbra boundary at photopheric heights, are converted into magnetic waves and steepen due to the strong density gradient.
Key words: Sun: abundances / Sun: atmosphere / Sun: magnetic fields / Sun: oscillations
Movie associated to Fig. 1 is available at https://www.aanda.org
© ESO 2021
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.