NONLINEAR FORCE-FREE FIELD EXTRAPOLATION OF A CORONAL MAGNETIC FLUX ROPE SUPPORTING A LARGE-SCALE SOLAR FILAMENT FROM A PHOTOSPHERIC VECTOR MAGNETOGRAM

AbstractInterest to lateral details of the solar filament shape named barbs, motivated by their relationship to filament chirality and helicity, showed their different orientation relative to the expected direction of the magnetic field. While the majority of barbs are stretched along the field, some barbs seem to be transversal to it and are referred to as anomalous barbs. We analyse the deformation of helical field lines by a small parasitic polarity using a simple flux rope model with a force-free field. A rather small and distant source of parasitic polarity stretches the bottom parts of the helical lines in its direction creating a lateral extension of dips below the flux-rope axis. They can be considered as normal barbs of the filament. A stronger and closer source of parasitic polarity makes the flux-rope field lines to be convex below its axis and creates narrow and deep dips near its position. As a result, the narrow structure, with thin threads across it, is formed whose axis is nearly perpendicular to the field. The structure resembles an anomalous barb. Hence, the presence of anomalous barbs does not contradict the flux-rope structure of a filament.

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Structure and Evolution of an Inter–Active Region Large-scale Magnetic Flux Rope

The Astrophysical Journal ◽

10.3847/1538-4357/abc701 ◽

2021 ◽

Vol 906 (1) ◽

pp. 45

Author(s):

Aiying Duan ◽

Chaowei Jiang ◽

Peng Zou ◽

Xueshang Feng ◽

Jun Cui

Keyword(s):

Active Region ◽

Magnetic Flux ◽

Large Scale ◽

Flux Rope ◽

Magnetic Flux Rope

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The magnetic flux rope structure of coronal mass ejections – 2021 Julius Bartels Medal Lecture at vEGU

10.5194/egusphere-egu21-11152 ◽

2021 ◽

Author(s):

Volker Bothmer

Keyword(s):

Magnetic Flux ◽

White Light ◽

Coronal Mass Ejections ◽

Large Scale ◽

Neutral Line ◽

Source Region ◽

Flux Rope ◽

Magnetic Clouds ◽

Small Scale ◽

Magnetic Flux Rope

<div> <p><span>Magnetic clouds are transient solar wind flows in the interplanetary medium with smooth rotations of the magnetic field vector and low plasma beta values. The analysis of magnetic clouds identified in the data of the two Helios spacecraft between 0.3 and 1 AU showed that they can be interpreted to first order by force-free, large-scale, cylindrical magnetic flux tubes. A close correlation of their occurrences was found with disappearing filaments at the Sun. The magnetic clouds that originated from the northern solar hemisphere showed predominantly left-handed magnetic helicities and the ones from the southern hemisphere predominantly right-handed ones. They were often preceded by an interplanetary shock wave and some were found to be directly following a coronal mass ejection towards the Helios spacecraft as detected by the Solwind coronagraph on board the P78-1 satellite. With the SOHO mission unprecedented long-term observations of coronal mass ejections (CMEs) were taken with the LASCO coronagraphs, with a spatial and time resolution that allowed to investigate their internal white-light fine structure. With complementary photospheric and EUV observations from SOHO, CMEs were found to arise from pre-existing small scale loop systems, overlying regions of opposite magnetic polarities. From the characteristic pattern of their source regions in both solar hemispheres, a generic scheme was presented in which their projected white-light topology depends primarily on the orientation and position of the source region&#8217;s neutral line on the solar disk. Based on this interpretation the graduated cylindrical shell method was developed, which allowed to model the electron density distribution of CMEs as 3D flux ropes. This concept was validated through stereoscopic observations of CMEs taken by the coronagraphs of the SECCHI remote sensing suite on board the twin STEREO spacecraft. The observations further revealed that the dynamic near-Sun evolution of CMEs often leads to distortions of their flux rope structure. However, the magnetic flux rope concept of CMEs is today one of the fundamental methods in space weather forecasts. With the Parker Solar Probe we currently observe for the first time CMEs in-situ and remotely at their birthplaces in the solar corona and can further unravel their origin and evolution from the corona into the heliosphere. This lecture provides a state-of-the-art overview on the magnetic structure of CMEs and includes latest observations from the Parker Solar Probe mission.</span></p> </div>

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Data-driven MHD Simulation of the Formation and Initiation of a Large-scale Preflare Magnetic Flux Rope in AR 12371

The Astrophysical Journal ◽

10.3847/1538-4357/ab75ab ◽

2020 ◽

Vol 892 (1) ◽

pp. 9 ◽

Cited By ~ 1

Author(s):

Wen He ◽

Chaowei Jiang ◽

Peng Zou ◽

Aiying Duan ◽

Xueshang Feng ◽

...

Keyword(s):

Magnetic Flux ◽

Large Scale ◽

Flux Rope ◽

Data Driven ◽

Mhd Simulation ◽

Magnetic Flux Rope

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Simulating the Coronal Evolution of Bipolar Active Regions to Investigate the Formation of Flux Ropes

Solar Physics ◽

10.1007/s11207-020-01749-2 ◽

2021 ◽

Vol 296 (1) ◽

Author(s):

S. L. Yardley ◽

D. H. Mackay ◽

L. M. Green

Keyword(s):

Magnetic Field ◽

Large Scale ◽

Initial Conditions ◽

Free Field ◽

Active Regions ◽

Coronal Magnetic Field ◽

Solar Dynamics Observatory ◽

Horizontal Magnetic Field ◽

Nonlinear Force ◽

Force Free Field

AbstractThe 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, Green, and van Ballegooijen (Astrophys. J. 729, 97, 2011). A time sequence of cleaned photospheric line-of-sight magnetograms, which covers the entire evolution of each AR, is used to drive the simulation. A comparison of the simulated coronal magnetic field with the 171 and 193 Å observations obtained by the Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA), is made for each AR by manual inspection. The results show that it is possible to reproduce the evolution of the main coronal features such as small- and large-scale coronal loops, filaments and sheared structures for 80% of the ARs. Varying the boundary and initial conditions, along with the addition of physical effects such as Ohmic diffusion, hyperdiffusion and a horizontal magnetic field injection at the photosphere, improves the match between the observations and simulated coronal evolution by 20%. The simulations were able to reproduce the build-up to eruption for 50% of the observed eruptions associated with the ARs. The mean unsigned time difference between the eruptions occurring in the observations compared to the time of eruption onset in the simulations was found to be ≈5 hrs. The simulations were particularly successful in capturing the build-up to eruption for all four eruptions that originated from the internal polarity inversion line of the ARs. The technique was less successful in reproducing the onset of eruptions that originated from the periphery of ARs and large-scale coronal structures. For these cases global, rather than local, nonlinear force-free field models must be used. While the technique has shown some success, eruptions that occur in quick succession are difficult to reproduce by this method and future iterations of the model need to address this.

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Tests and applications of nonlinear force-free field extrapolations in spherical geometry

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313003190 ◽

2012 ◽

Vol 8 (S294) ◽

pp. 553-554

Author(s):

Y. Guo ◽

M. D. Ding

Keyword(s):

Magnetic Field ◽

Analytical Solution ◽

Large Scale ◽

Initial Conditions ◽

Free Field ◽

Spherical Geometry ◽

Source Surface ◽

Field Source ◽

Nonlinear Force ◽

Force Free Field

AbstractWe test a nonlinear force-free field (NLFFF) optimization code in spherical geometry with an analytical solution from Low and Lou. The potential field source surface (PFSS) model is served as the initial and boundary conditions where observed data are not available. The analytical solution can be well recovered if the boundary and initial conditions are properly handled. Next, we discuss the preprocessing procedure for the noisy bottom boundary data, and find that preprocessing is necessary for NLFFF extrapolations when we use the observed photospheric magnetic field as bottom boundaries. Finally, we apply the NLFFF model to a solar area where four active regions interacting with each other. An M8.7 flare occurred in one active region. NLFFF modeling in spherical geometry simultaneously constructs the small and large scale magnetic field configurations better than the PFSS model does.

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Multiple Magnetic Reconnections Driven by a Large-scale Magnetic Flux Rope

The Astrophysical Journal ◽

10.3847/1538-4357/ab01cf ◽

2019 ◽

Vol 873 (1) ◽

pp. 23 ◽

Cited By ~ 6

Author(s):

G. P. Zhou ◽

C. M. Tan ◽

Y. N. Su ◽

C. L. Shen ◽

B. L. Tan ◽

...

Keyword(s):

Magnetic Flux ◽

Large Scale ◽

Flux Rope ◽

Magnetic Flux Rope

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Modeling Magnetic Flux Ropes

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313010843 ◽

2013 ◽

Vol 8 (S300) ◽

pp. 121-124

Author(s):

Chun Xia ◽

Rony Keppens

Keyword(s):

Magnetic Flux ◽

Large Scale ◽

Thermal Structure ◽

Three Dimensional ◽

Lower Boundary ◽

Flux Rope ◽

Mhd Simulation ◽

Magnetic Flux Rope ◽

Polarity Inversion ◽

Magnetic Flux Ropes

AbstractThe magnetic configuration hosting prominences can be a large-scale helical magnetic flux rope. As a necessary step towards future prominence formation studies, we report on a stepwise approach to study flux rope formation. We start with summarizing our recent three-dimensional (3D) isothermal magnetohydrodynamic (MHD) simulation where a flux rope is formed, including gas pressure and gravity. This starts from a static corona with a linear force-free bipolar magnetic field, altered by lower boundary vortex flows around the main polarities and converging flows towards the polarity inversion. The latter flows induce magnetic reconnection and this forms successive new helical loops so that a complete flux rope grows and ascends. After stopping the driving flows, the system relaxes to a stable helical magnetic flux rope configuration embedded in an overlying arcade. Starting from this relaxed isothermal endstate, we next perform a thermodynamic MHD simulation with a chromospheric layer inserted at the bottom. As a result of a properly parametrized coronal heating, and due to radiative cooling and anisotropic thermal conduction, the system further relaxes to an equilibrium where the flux rope and the arcade develop a fully realistic thermal structure. This paves the way to future simulations for 3D prominence formation.

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Numerical simulations of the CME on 2010 April 8

Proceedings of the International Astronomical Union ◽

10.1017/s174392131300327x ◽

2012 ◽

Vol 8 (S294) ◽

pp. 575-576

Author(s):

Yingna Su ◽

Bernhard Kliem ◽

Adriaan van Ballegooijen ◽

Edward Deluca

Keyword(s):

Magnetic Field ◽

Stable Equilibrium ◽

Free Field ◽

Flux Rope ◽

Stable Model ◽

Mhd Simulations ◽

Insertion Method ◽

Ideal Mhd ◽

Nonlinear Force ◽

Force Free Field

AbstractWe present 3D zero-beta ideal MHD simulations of the solar flare/CME event that occurred in Active Region 11060 on 2010 April 8. The initial magnetic configurations of the two simulations are stable nonlinear force-free field and unstable magnetic field models constructed by Su et al. (2011) using the flux rope insertion method. The MHD simulations confirm that the stable model relaxes to a stable equilibrium, while the unstable model erupts as a CME. Comparisons between observations and MHD simulations of the CME are also presented.

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