Data-optimized coronal field model: 1. Proof of concept

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Thursday, August 8, 2019

Deriving the strength and direction of the three-dimensional (3D) magnetic field in the solar atmosphere is fundamental for understanding its dynamics. Volume information on the magnetic field mostly relies on photospheric and/or chromospheric surface vector magnetic fields.

Graphic depicting field-lines from a ground-truth flux-rope magnetic field model
Top view of selected field-lines from a ground-truth flux-rope magnetic field model and the optimization solution obtained by using the DOCFM framework to match Stokes polarimetric (synthetic) observations. The field-lines from the DOCFM solutions were all integrated from the same starting footpoints as the ground-truth magnetic field lines. A few colored arrows have been added to emphasize regions where magnetic field lines are different from the ground-truth magnetic field ones.

Infrared coronal polarimetry could provide additional information to better constrain magnetic field reconstructions. However, combining such data with reconstruction methods is challenging, e.g., because of the optical-thinness of the solar corona and the lack and limitations of stereoscopic polarimetry. To address these issues, we introduce the Data-Optimized Coronal Field Model (DOCFM) framework, a model-data fitting approach that combines a parametrized 3D generative model, e.g., a magnetic field extrapolation or a magnetohydrodynamic model, with forward modeling of coronal data. We test it with a parametrized flux rope insertion method and infrared coronal polarimetry where synthetic observations are created from a known "ground truth" physical state. We show that this framework allows us to retrieve the 3D magnetic field with high accuracy when the coronal polarization dataset to be fitted (the ground truth) originates from a solution of the generative model. In observational studies, the DOCFM will provide a means to force the solutions derived with dierent reconstruction methods to satisfy additional, common, coronal constraints. The DOCFM framework therefore opens new perspectives for the exploitation of coronal polarimetry in magnetic field reconstructions and for developing new techniques to more reliably infer the 3D magnetic fields that trigger solar flares and coronal mass ejections.

Publication Name: Astrophysical Journal
First HAO Author's Name: Sarah Gibson

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