Non-LTE inversions of a confined X2.2 flare: I. Vector magnetic field in the photosphere and chromosphere : I. The vector magnetic field in the photosphere and chromosphere

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Vissers , G J M , Danilovic , S , de la Cruz Rodriguez , J , Leenaarts , J , Morosin , R , Diaz Baso , C , Reid , A , Pomoell , J , Price , D & Inoue , S 2020 , ' Non-LTE inversions of a confined X2.2 flare: I. Vector magnetic field in the photosphere and chromosphere : I. The vector magnetic field in the photosphere and chromosphere ' , Astronomy & Astrophysics , vol. 645 , 1 . https://doi.org/10.1051/0004-6361/202038900

Title: Non-LTE inversions of a confined X2.2 flare: I. Vector magnetic field in the photosphere and chromosphere : I. The vector magnetic field in the photosphere and chromosphere
Author: Vissers, G. J. M.; Danilovic, S.; de la Cruz Rodriguez, J.; Leenaarts, J.; Morosin, R.; Diaz Baso, C.; Reid, A.; Pomoell, Jens; Price, Daniel; Inoue, S.
Contributor: University of Helsinki, Department of Physics
University of Helsinki, Space Physics Research Group
Date: 2020-12-21
Language: eng
Number of pages: 15
Belongs to series: Astronomy & Astrophysics
ISSN: 1432-0746
URI: http://hdl.handle.net/10138/324592
Abstract: Obtaining the magnetic field vector accurately in the solar atmosphere is essential for studying changes in field topology during flares and to reliably model space weather. We tackle this problem by applying various inversion methods to a confined X2.2 flare in NOAA AR 12673 on September 6, 2017, comparing the photospheric and chromospheric magnetic field vector with those from two numerical models of this event. We obtain the photospheric field from Milne-Eddington (ME) and (non-)local thermal equilibrium (non-LTE) inversions of Hinode SOT/SP Fe I 6301.5Å and 6302.5Å. The chromospheric field is obtained from a spatially-regularised weak field approximation (WFA) and non-LTE inversions of Ca II 8542Å observed with CRISP at the Swedish 1-m Solar Telescope. The LTE- and non-LTE-inferred photospheric field components are strongly correlated throughout the atmosphere, with stronger field and higher temperatures in the non-LTE inversions. For the chromospheric field, the non-LTE inversions correlate well with the spatially-regularised WFA. We find strong-field patches of over 4.5 kG in the photosphere, co-located with similar concentrations exceeding 3 kG in the chromosphere. The obtained field strengths are up to 2-3 times higher than in the numerical models, with more concentrated and structured photosphere-to-chromosphere shear close to the polarity inversion line. The LTE and non-LTE Fe I inversions yield essentially the same photospheric field, while ME inversions fail to reproduce the field vector orientation where Fe I is in emission. Our inversions confirm the locations of flux rope footpoints that are predicted by numerical models. However, pre-processing and lower spatial resolution lead to weaker and smoother field in the models than what the data indicate. This emphasises the need for higher spatial resolution in the models to better constrain pre-eruptive flux ropes.
Subject: 115 Astronomy, Space science
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