Forced Field Extrapolation: Testing a Magnetohydrodynamic (Mhd) Relaxation Method With a Flux-Rope Emergence Model

Zhu, Xiaoshuai; Wang, H. N.; Du, Zhanle; Fan, Yaofu

doi:10.1088/0004-637x/768/2/119

Cited by 44 publications

(40 citation statements)

References 17 publications

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“…Compared with the work of Zhu et al (2013), the viscous velocity term is replaced by a velocity damping term as the velocity cannot be effectively dissipated by the former. The large velocity produced by the strong forced magnetic field of the AR leads to a failed extrapolation.…”

Section: Methodsmentioning

confidence: 99%

“…Anther modification is the elimination of ·  B. In Zhu et al (2013), Powell's source terms (Powell et al 1999) are applied to prevent the accumulation of ·  B from propagating the "magnetic monopoles" with the flow. In this paper, the project scheme originally proposed by Brackbill & Barnes (1980) is further used to eliminate the ·  B error.…”

Section: Methodsmentioning

confidence: 99%

“…As noted by Zhu et al (2013), it is important to choose a reasonable starting height for the atmosphere model as the initial condition to adapt the magnetogram. If the starting height is too low, then it is difficult to drive the heavy plasma, which results in a too long relaxation time.…”

Section: Methodsmentioning

confidence: 99%

“…They found, under a modest spatial resolution of 2″, that the field lines are mostly in agreement with fibrils, exhibiting some misalignments. Zhu et al (2013) presented a new implementation of the magnetohydrodynamics (MHD) relaxation method to extrapolate the magnetic field on the Sun. In this method, a high β region like the photosphere near the bottom boundary is introduced by setting a Sun-like atmosphere model as the initial condition.…”

Section: Introductionmentioning

confidence: 99%

“…In this paper, we report modifications of the forced field extrapolation with respect to the version of Zhu et al (2013) and its application to reconstructing the magnetic field in the chromosphere of AR 11967 using Solar Dynamics Observatory/Helioseismic and Magnetic Imager (SDO/HMI; Schou et al 2012) magnetograms as input. Only the magnetic field in the chromosphere is considered as the chromosphere is a more forced region than the corona and the spatial resolution of the Hα images can reach 0 16 ).…”

Section: Introductionmentioning

confidence: 99%

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FORCED FIELD EXTRAPOLATION OF THE MAGNETIC STRUCTURE OF THE Hα FIBRILS IN THE SOLAR CHROMOSPHERE

Zhu

Wang

et al. 2016

ApJ

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We present a careful assessment of forced field extrapolation using the Solar Dynamics Observatory/Helioseismic and Magnetic Imager magnetogram. We use several metrics to check the convergence property. The extrapolated field lines below 3600 km appear to be aligned with most of the Hα fibrils observed by the New Vacuum Solar Telescope. In the region where magnetic energy is far larger than potential energy, the field lines computed by forced field extrapolation are still consistent with the patterns of Hα fibrils while the nonlinear force-free field results show a large misalignment. The horizontal average of the lorentz force ratio shows that the forced region where the force-free assumption fails can reach heights of 1400-1800 km. The non-force-free state of the chromosphere is also confirmed based on recent radiation magnetohydrodynamics simulations.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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FORCED FIELD EXTRAPOLATION OF THE MAGNETIC STRUCTURE OF THE Hα FIBRILS IN THE SOLAR CHROMOSPHERE

Zhu

Wang

et al. 2016

ApJ

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Automatic Computation of Linear Magneto-Hydro-Static Equilibria

Wiegelmann

Madjarska

2023

Sol Phys

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Deriving the physical parameters of observed phenomena in the solar atmosphere has fundamental importance, as these parameters are then employed to constrain and validate models. Here we report the development of a new computational algorithm based on a magneto-hydro-static model that computes the magnetic field in the solar atmosphere and automatically matches individual magnetic-field lines with observed structures that appear with enhanced emission in extreme-ultraviolet (EUV) images. Presently, for the quiet-Sun regions, we can only measure the vertical photospheric magnetic field $B_{z}$ B z , as accurate horizontal magnetic field measurements are not available. Thus, vertical photospheric magnetic-field measurements are extrapolated into the upper atmosphere, from the photosphere to the corona, with a magneto-hydro-static model. Free model parameters are then optimized with a downhill-simplex method by comparing quantitatively magnetic-field lines with the enhanced emission of loop structures composing the so-called coronal bright points recorded in EUV images taken with the Atmospheric Imaging Assembly on-board the Solar Dynamics Observatory. The algorithm will be applicable to any solar image data where individual structures with an enhanced emission can be resolved. Most importantly, the algorithm can be employed to obtain the magnetic properties of these structures above the photosphere.

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Solar Ultraviolet Bursts

et al. 2018

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The term "ultraviolet (UV) burst" is introduced to describe small, intense, transient brightenings in ultraviolet images of solar active regions. We inventorize their properties and provide a definition based on image sequences in transition-region lines. Coronal signatures are rare, and most bursts are associated with small-scale, canceling oppositepolarity fields in the photosphere that occur in emerging flux regions, moving magnetic features in sunspot moats, and sunspot light bridges. We also compare UV bursts with similar transition-region phenomena found previously in solar ultraviolet spectrometry and with similar phenomena at optical wavelengths, in particular Ellerman bombs. Akin to the lat-Electronic supplementary material The online version of this article (https://doi.

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Forced Field Extrapolation: Testing a Magnetohydrodynamic (Mhd) Relaxation Method With a Flux-Rope Emergence Model

Cited by 44 publications

References 17 publications

FORCED FIELD EXTRAPOLATION OF THE MAGNETIC STRUCTURE OF THE Hα FIBRILS IN THE SOLAR CHROMOSPHERE

FORCED FIELD EXTRAPOLATION OF THE MAGNETIC STRUCTURE OF THE Hα FIBRILS IN THE SOLAR CHROMOSPHERE

Automatic Computation of Linear Magneto-Hydro-Static Equilibria

Solar Ultraviolet Bursts

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