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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 developed a new nonlinear force-free magnetic field (NLFFF) forward-fitting algorithm based on an analytical approximation of force-free and divergence-free NLFFF solutions, which requires as input a line-of-sight magnetogram and traced…

Solar and Stellar Astrophysics · Physics 2013-05-24 Markus J. Aschwanden

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

We have reported previously on a new method we are developing for using image-based information to improve global coronal magnetic field models. In that work we presented early tests of the method which proved its capability to improve…

Solar and Stellar Astrophysics · Physics 2017-08-02 Shaela I. Jones , Joseph M. Davila , Vadim M. Uritsky

Reliable measurements of the solar magnetic field are still restricted to the photosphere, and our present knowledge of the three-dimensional coronal magnetic field is largely based on extrapolation from photospheric magnetogram using…

Solar and Stellar Astrophysics · Physics 2015-06-05 Chaowei Jiang , Xueshang Feng , Changqing Xiang

Magnetic Particle Imaging (MPI) is a promising noninvasive in vivo imaging modality that makes it possible to map the spatial distribution of superparamagnetic nanoparticles by exposing them to dynamic magnetic fields. In the Field-Free…

Numerical Analysis · Mathematics 2025-08-08 Vladyslav Gapyak , Thomas März , Andreas Weinmann

Magnetic fields in the solar corona are responsible for a wide range of phenomena. However, any direct measurements of the coronal magnetic fields are very difficult due to lack of suitable spectral lines, weak magnetic fields, and high…

Solar and Stellar Astrophysics · Physics 2013-10-28 P. Vemareddy , A. Ambastha , T. Wiegelmann

Coronal holes (CHs) are regions with unbalanced magnetic flux, and have been associated with open magnetic field (OMF) structures. However, it has been reported that some CHs do not intersect with OMF regions. To investigate the…

Solar and Stellar Astrophysics · Physics 2022-07-27 Guan-Han Huang , Chia-Hsien Lin , Lou-Chuang Lee

With the development of new instrumentation providing measurements of solar photospheric vector magnetic fields, we need to develop our understanding of the effects of current density on coronal magnetic field configurations. The object is…

Astrophysics · Physics 2009-11-13 S. Regnier , E. R. Priest

The coronal magnetic field evolution of 20 bipolar active regions (ARs) is simulated from their emergence to decay using the time-dependent nonlinear force-free field method of Mackay et al. A time sequence of cleaned photospheric…

Solar and Stellar Astrophysics · Physics 2021-01-13 Stephanie L. Yardley , Duncan H. Mackay , Lucie M. Green

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

Non-linear force-free extrapolations are a common approach to estimate the 3D topology of coronal magnetic fields based on photospheric vector magnetograms. The force-free assumption is a valid approximation at coronal heights, but for the…

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

A 3D tomographic reconstruction technique is described for inversion of a set of limited-angle high-resolution 2D visible light emission projections (extended in the vertical and toroidal directions) of global MHD eigenmodes in the H-1NF…

Plasma Physics · Physics 2014-08-29 S. R. Haskey , B. D. Blackwell , B. Seiwald , J. Howard

Photospheric electric fields, estimated from sequences of vector magnetic field and Doppler measurements, can be used to estimate the flux of magnetic energy (the Poynting flux) into the corona and as time-dependent boundary conditions for…

Solar and Stellar Astrophysics · Physics 2014-10-13 Maria D. Kazachenko , George H. Fisher , Brian T. Welsch

We present a novel magnetohydrostatic numerical model that solves directly for the force-balanced magnetic field in the solar corona. This model is constructed with Radial Basis Function Finite Differences (RBF-FD), specifically 3D…

Solar and Stellar Astrophysics · Physics 2022-05-11 Nathaniel H. Mathews , Natasha Flyer , Sarah E. Gibson

We develop an approach of Grad-Shafranov (GS) reconstruction for toroidal structures in space plasmas, based on in-situ spacecraft measurements. The underlying theory is the GS equation that describes two-dimensional magnetohydrostatic…

Solar and Stellar Astrophysics · Physics 2017-08-30 Qiang Hu

The rapid, irreversible change of the photospheric magnetic field has been recognized as an important element of the solar flare process. This Letter reports such a rapid change of magnetic fields during the 2011 February 13 M6.6 flare in…

Solar and Stellar Astrophysics · Physics 2015-06-03 Chang Liu , Na Deng , Rui Liu , Jeongwoo Lee , Thomas Wiegelmann , Ju Jing , Yan Xu , Shuo Wang , Haimin Wang

We report Tensorial tomographic Fourier Ptychography (ToFu), a new non-scanning label-free tomographic microscopy method for simultaneous imaging of quantitative phase and anisotropic specimen information in 3D. Built upon Fourier…

We derive a new 3D model for magnetic particle imaging (MPI) that is able to incorporate realistic magnetic fields in the reconstruction process. In real MPI scanners, the generated magnetic fields have distortions that lead to deformed…

Numerical Analysis · Mathematics 2020-12-30 Gaël Bringout , Wolfgang Erb , Jürgen Frikel