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Wiegelmann, T.; Inhester, B.

doi:10.1023/a:1024282131117

Cited by 42 publications

(26 citation statements)

References 22 publications

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“…Some basic steps have been taken already with a tomography program developed by Wiegelmann & Inhester (2003), which provides the 3D plasma density structure more directly, e.g. by using coronagraph images from different viewpoints, as provided by the STEREOmission, for a tomographic inversion.…”

Section: Discussionmentioning

confidence: 99%

A first step in reconstructing the solar corona self-consistently with a magnetohydrostatic model during solar activity minimum

Ruan¹,

Wiegelmann²,

Inhester³

et al. 2008

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Aims. We compute the distribution of the magnetic field and the plasma in the global corona with a self-consistent magnetohydrostatic (MHS) model. Methods. Because direct measurements of the solar coronal magnetic field and plasma are extremely difficult and inaccurate, we use a modeling approach based on observational quantities, e.g. the measured photospheric magnetic field, to reconstruct the structure of the global solar corona. We take an analytic magnetohydrostatic model to extrapolate the magnetic field in the corona from photospheric magnetic field measurement. In the model, the electric current density can be decomposed into two components: one component is aligned with the magnetic field lines, whereas the other component flows in spherical shells. The second component of the current produces finite Lorentz forces that are balanced by the pressure gradient and the gravity force. We derive the 3D distribution of the magnetic field and plasma self-consistently in one model. The boundary conditions are given by a synoptic magnetogram on the inner boundary and by a source surface model at the outer boundary. Results. The density in the model is higher in the equatorial plane than in the polar region. We compare the magnetic field distribution of our model with potential and force-free field models for the same boundary conditions and find that our model differs noticeably from both. We discuss how to apply the model and how to improve it.

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Section: Discussionmentioning

confidence: 99%

A first step in reconstructing the solar corona self-consistently with a magnetohydrostatic model during solar activity minimum

Ruan¹,

Wiegelmann²,

Inhester³

et al. 2008

A&A

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“…Let us remark that the structure identification method by magnetic field lines provides already a 3D structure of the loop which might be further refined by stereoscopic methods. In particular, the advent of the STEREO mission has produced an increased interest of the solar physics community in stereoscopic (Aschwanden et al,1999 and tomographic techniques (Zidowitz, 1999;Frazin, 2000;Wiegelmann & Inhester, 2003) used in other branches of physics, image and information sciences. However, unlike many of the "experiments" conducted in the latter disciplines, the STEREO mission does not provide sufficient control over many of the parameters which determine the conditions for an optimal 3D reconstruction.…”

Section: Discussionmentioning

confidence: 99%

How To Use Magnetic Field Information For Coronal Loop Identification

et al. 2005

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Abstract. The structure of the solar corona is dominated by the magnetic field because the magnetic pressure is about four orders of magnitude higher than the plasma pressure. Due to the high conductivity the emitting coronal plasma (visible e.g. in SOHO/EIT) outlines the magnetic field lines. The gradient of the emitting plasma structures is significantly lower parallel to the magnetic field lines than in the perpendicular direction. Consequently information regarding the coronal magnetic field can be used for the interpretation of coronal plasma structures. We extrapolate the coronal magnetic field from photospheric magnetic field measurements into the corona. The extrapolation method depends on assumptions regarding coronal currents, e.g. potential fields (current free) or force-free fields (current parallel to magnetic field). As a next step we project the reconstructed 3D magnetic field lines on an EIT-image and compare with the emitting plasma structures. Coronal loops are identified as closed magnetic field lines with a high emissivity in EIT and a small gradient of the emissivity along the magnetic field.

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“…We solve these equations with the help of an optimization principle, as proposed by Wheatland et al (2000) and generalized by Wiegelmann & Inhester (2003). We define the functional…”

Section: Methodsmentioning

confidence: 99%

Testing non-linear force-free coronal magnetic field extrapolations with the Titov-Démoulin equilibrium

Wiegelmann¹,

Inhester²,

Kliem

et al. 2006

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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 code with the help of a known analytical solution.Methods. The non-linear force-free equations are numerically solved with the help of an optimization principle. The method minimizes an integral over the force-free and solenoidal condition. As boundary condition we use either the magnetic field components on all six sides of the computational box in Case I or only on the bottom boundary in Case II. We check the quality of the reconstruction by computing how well force-freeness and divergence-freeness are fulfilled and by comparing the numerical solution with the analytical solution. The comparison is done with magnetic field line plots and several quantitative measures, like the vector correlation, Cauchy Schwarz, normalized vector error, mean vector error and magnetic energy. Results. For Case I the reconstructed magnetic field shows good agreement with the original magnetic field topology, whereas in Case II there are considerable deviations from the exact solution. This is corroborated by the quantitative measures, which are significantly better for Case I. Conclusions. Despite the strong nonlinearity of the considered force-free equilibrium, the optimization method of extrapolation is able to reconstruct it; however, the quality of reconstruction depends significantly on the consistency of the input data, which is given only if the known solution is provided also at the lateral and top boundaries, and on the presence or absence of flux concentrations near the boundaries of the magnetogram.

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Untitled

Cited by 42 publications

References 22 publications

A first step in reconstructing the solar corona self-consistently with a magnetohydrostatic model during solar activity minimum

A first step in reconstructing the solar corona self-consistently with a magnetohydrostatic model during solar activity minimum

How To Use Magnetic Field Information For Coronal Loop Identification

Testing non-linear force-free coronal magnetic field extrapolations with the Titov-Démoulin equilibrium

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