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CONTEXT: As the coronal magnetic field can usually not be measured directly, it has to be extrapolated from photospheric measurements into the corona. AIMS: We test the quality of a non-linear force-free coronal magnetic field extrapolation…

For the extrapolation of magnetic fields into the solar corona from measurements taken in the photosphere (or chromosphere) force-free magnetic fields are typically used. This does not take into account that the lower layers of the solar…

Solar and Stellar Astrophysics · Physics 2020-01-08 Thomas Neukirch , Thomas Wiegelmann

The magnetic field permeating the solar atmosphere is generally thought to provide the energy for much of the activity seen in the solar corona, such as flares, coronal mass ejections (CMEs), etc. To overcome the unavailability of coronal…

Solar and Stellar Astrophysics · Physics 2015-06-17 Tilaye Tadesse , T. Wiegelmann , S. Gosain , P. MacNeice , Alexei A. Pevtsov

Modeling the interface region between solar photosphere and corona is challenging, because the relative importance of magnetic and plasma forces change by several orders of magnitude. While the solar corona can be modeled by the force-free…

Solar and Stellar Astrophysics · Physics 2018-10-31 Xiaoshuai Zhu , Thomas Wiegelmann

Conventional MRI reconstruction methods treat images and coil sensitivities as discrete objects, leading to high memory demands and limited structural awareness that hamper effective regularization. These limitations hinder accurate…

Image and Video Processing · Electrical Eng. & Systems 2026-05-12 Ray Sheombarsing , Max van Riel , David Heesterbeek , Nico van den Berg , Alessandro Sbrizzi

This work examines the relation between the fractal properties of the photospheric magnetic patterns and those of the coronal magnetic fields in solar active regions.Our results show no correlation between the fractal dimensions of the…

Solar and Stellar Astrophysics · Physics 2015-05-14 M. Dimitropoulou , M. Georgoulis , H. Isliker , L. Vlahos , A. Anastasiadis , D. Strintzi , X. Moussas

We use SDO/HMI and SOLIS/VSM photospheric magnetic field measurements to model the force-free coronal field above a solar active region, assuming magnetic forces to dominate. We take measurement uncertainties caused by, e.g., noise and the…

Solar and Stellar Astrophysics · Physics 2015-06-05 J. K. Thalmann , A. Pietarila , X. Sun , T. Wiegelmann

The coronal magnetic field directly or indirectly affects a majority of the phenomena studied in space physics. It provides energy for coronal heating, controls the release of coronal mass ejections (CMEs), and drives heliospheric and…

Solar and Stellar Astrophysics · Physics 2016-04-13 Shaela I. Jones , Joseph M. Davila , Vadim M. Uritsky

Large-scale coronal plasma evolutions can be adequately described by magnetohydrodynamics (MHD) equations. However, full multi-dimensional MHD simulations require substantial computational resources. Given the low plasma $\beta$ in the…

Solar and Stellar Astrophysics · Physics 2024-04-29 Yuhao Zhou , Xiaohong Li , Rony Keppens

The nonlinear force-free field (NLFFF) modeling has been extensively used as a tool to infer three-dimensional (3D) magnetic field structure. In this study, the dependency of the NLFFF calculation with respect to the initial guess of the 3D…

Solar and Stellar Astrophysics · Physics 2020-06-09 Y. Kawabata , S. Inoue , T. Shimizu

Nonlinear Force-free Field (NLFFF) models are widely used to investigate coronal magnetic field structure in solar active regions, but methods to validate them remain limited. Here, we use Gaussian separation, recently applied to solar…

Solar and Stellar Astrophysics · Physics 2026-05-12 Abhinav G. Iyer , Michael S. Wheatland , Brian T. Welsch , Yang Liu , S. A. Gilchrist

It is widely believed that loops observed in the solar atmosphere trace out magnetic field lines. However, the degree to which magnetic field extrapolations yield field lines that actually do follow loops has yet to be studied…

Solar and Stellar Astrophysics · Physics 2018-06-27 Harry P. Warren , Nicholas A. Crump , Ignacio Ugarte-Urra , Xudong Sun , Markus J. Aschwanden , Thomas Wiegelmann

In this study, photospheric vector magnetograms obtained with the Synoptic Optical Long-term Investigations of the Sun survey (SOLIS), are used as boundary conditions to model the three-dimensional nonlinear force-free (NLFF) coronal…

Solar and Stellar Astrophysics · Physics 2015-05-30 Tilaye Tadesse , T. Wiegelmann , B. Inhester , A. Pevtsov

The 3D structure of an active region (AR) filament is studied using nonlinear force-free field (NLFFF) extrapolations based on simultaneous observations at a photospheric and a chromospheric height. To that end, we used the Si I 10827 \AA\…

Solar and Stellar Astrophysics · Physics 2015-06-03 L. Yelles Chaouche , C. Kuckein , V. Martínez Pillet , F. Moreno-Insertis

In this review, I focus on the structure and evolution of the coronal magnetic fields modelled from observations. The development of instruments measuring the photospheric and chromospheric magnetic fields with a high spatial and time…

Solar and Stellar Astrophysics · Physics 2011-01-18 Stephane Regnier

In the recent years, global coronal models have experienced an ongoing increase in popularity as tools for forecasting solar weather. Within the domain of up to 21.5Rsun, magnetohydrodynamics (MHD) is used to resolve the coronal structure…

Solar and Stellar Astrophysics · Physics 2022-11-30 Michaela Brchnelova , Błażej Kuźma , Barbara Perri , Andrea Lani , Stefaan Poedts

We investigate the recently quantified misalignment of $\alpha_{mis} \approx 20^\circ-40^\circ$ between the 3-D geometry of stereoscopically triangulated coronal loops observed with STEREO/EUVI (in four active regions) and theoretical…

Solar and Stellar Astrophysics · Physics 2015-05-18 Markus J. Aschwanden , Anne W. Sandman

Magnetic particle imaging (MPI) is a tracer-based imaging modality that detects superparamagnetic iron oxide nanoparticles in vivo, with applications in cancer cell tracking, lymph node mapping, and cell therapy monitoring. We introduce a…

Time-evolving magnetohydrodynamic (MHD) coronal modeling, driven by a series of time-dependent photospheric magnetograms, represents a new generation of coronal simulations. This approach offers greater realism compared to traditional…

In the solar corona, magnetic flux rope is believed to be a fundamental structure accounts for magnetic free energy storage and solar eruptions. Up to the present, the extrapolation of magnetic field from boundary data is the primary way to…

Solar and Stellar Astrophysics · Physics 2016-01-20 Chaowei Jiang , Xueshang Feng