A Non-Linear Force-Free Field Model for the Evolving Magnetic Structure of Solar Filaments

Solar Physics ◽  
2009 ◽  
Vol 260 (2) ◽  
pp. 321-346 ◽  
Author(s):  
Duncan H. Mackay ◽  
A. A. van Ballegooijen
Keyword(s):  
Magnetic Structure ◽  
Field Model ◽  
Free Field ◽  
Non Linear ◽  
Solar Filaments ◽  
Linear Force ◽  
Force Free Field

Various Barbs in Solar Filaments

2017 ◽  
Vol 34 ◽  
Author(s):  
Boris Filippov
Keyword(s):  
Free Field ◽  
Flux Rope ◽  
Lateral Extension ◽  
Solar Filaments ◽  
Solar Filament ◽  
Field Lines ◽  
The Magnetic Field ◽  
Narrow Structure ◽  
Force Free Field ◽  
Helical Field

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.

scholarly journals Topological study of active region 11158

2013 ◽  
Vol 8 (S300) ◽  
pp. 479-480
Author(s):  
Jie Zhao ◽  
Hui Li ◽  
Etienne Pariat ◽  
Brigitte Schmieder ◽  
Yang Guo ◽  
...  
Keyword(s):  
Active Region ◽  
Magnetic Fields ◽  
Free Field ◽  
Three Dimensional ◽  
Projection Data ◽  
Solar Dynamics Observatory ◽  
Equal Area ◽  
Linear Force ◽  
Solar Dynamics ◽  
Force Free Field

AbstractWith the cylindrical equal area (CEA) projection data from the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO), we reconstructed the three-dimensional (3D) magnetic fields in the corona, using a non-linear force-free field (NLFFF) extrapolation method every 12 minutes during five days, to calculate the squashing degree factor Q in the volume. The results show that this AR has an hyperbolic flux tube (HFT) configuration, a typical topology of quadrupole, which is stable even during the two large flares (M6.6 and X2.2 class flares).

scholarly journals Magnetic Structure in Successively Erupting Active Regions: Comparison of Flare-Ribbons With Quasi-Separatrix Layers

2021 ◽  
Vol 9 ◽  
Author(s):  
P. Vemareddy
Keyword(s):  
Magnetic Structure ◽  
Free Field ◽  
Flux Rope ◽  
Active Regions ◽  
Peak Time ◽  
Vector Magnetic Field ◽  
Core Field ◽  
The Core ◽  
Frame Work ◽  
Force Free Field

This paper studies the magnetic topology of successively erupting active regions (ARs) 11,429 and 12,371. Employing vector magnetic field observations from Helioseismic and Magnetic Imager, the pre-eruptive magnetic structure is reconstructed by a model of non-linear force-free field (NLFFF). For all the five CMEs from these ARs, the pre-eruptive magnetic structure identifies an inverse-S sigmoid consistent with the coronal plasma tracers in EUV observations. In all the eruption cases, the quasi-separatrix layers (QSLs) of large Q values are continuously enclosing core field bipolar regions in which inverse-S shaped flare ribbons are observed. These QSLs essentially represent the large connectivity gradients between the domains of twisted core flux within the inner bipolar region and the surrounding potential like arcade. It is consistent with the observed field structure largely with the sheared arcade. The QSL maps in the chromosphere are compared with the flare-ribbons observed at the peak time of the flares. The flare ribbons are largely inverse-S shape morphology with their continuity of visibility is missing in the observations. For the CMEs in the AR 12371, the QSLs outline the flare ribbons as a combination of two inverse J-shape sections with their straight parts being separated. These QSLs are typical with the weakly twisted flux rope. Similarly, for the CMEs in the AR 11429, the QSLs are co-spatial with the flare ribbons both in the middle of the PIL and in the hook sections. In the frame work of standard model of eruptions, the observed flare ribbons are the characteristic of the pre-eruptive magnetic structure being sigmoid which is reproduced by the NLFFF model with a weakly twisted flux rope at the core.

scholarly journals Force-Free Models of Filament Channels

1998 ◽  
Vol 167 ◽  
pp. 274-277
Author(s):  
A.W. Longbottom
Keyword(s):  
Magnetic Fields ◽  
Multigrid Method ◽  
Flux Distribution ◽  
Free Field ◽  
Idealized Model ◽  
System A ◽  
Filament Channel ◽  
Linear Force ◽  
Field Lines ◽  
Force Free Field

AbstractA fast multigrid method to calculate the linear force-free field for a prescribed photospheric flux distribution is outlined. This is used to examine an idealized model of a filament channel. The magnetic fields, for a number of different field strengths and positions, are calculated and the height up to which field lines connect along the channel is examined. This is shown to strongly depend on the value of the helicity of the system. A possible explanation, in terms of the global helicity of the system, is suggested for the dextral/sinistral hemispheric pattern observed in filament channels.

SIGMOIDAL ACTIVE REGION ON THE SUN: COMPARISON OF A MAGNETOHYDRODYNAMICAL SIMULATION AND A NONLINEAR FORCE-FREE FIELD MODEL

2012 ◽  
Vol 750 (1) ◽  
pp. 15 ◽  
Author(s):  
A. Savcheva ◽  
E. Pariat ◽  
A. van Ballegooijen ◽  
G. Aulanier ◽  
E. DeLuca
Keyword(s):  
Active Region ◽  
Field Model ◽  
Free Field ◽  
The Sun ◽  
Nonlinear Force ◽  
Force Free Field

A Better Linear Force‐free Field

1999 ◽  
Vol 518 (2) ◽  
pp. 948-953 ◽  
Author(s):  
M. S. Wheatland
Keyword(s):  
Free Field ◽  
Linear Force ◽  
Force Free Field

Comments on “Comments on Solar Linear Force-Free Field and Application of FFT Analysis”

2006 ◽  
Vol 30 (3) ◽  
pp. 311-315
Author(s):  
Li Zhu-heng ◽  
Yan Yi-hua ◽  
Song Guo-xiang
Keyword(s):  
Free Field ◽  
Linear Force ◽  
Force Free Field ◽  
Fft Analysis

scholarly journals Magnetohydrodynamic study on the effect of the gravity stratification on flux rope ejections

2013 ◽  
Vol 8 (S300) ◽  
pp. 197-200
Author(s):  
Paolo Pagano ◽  
Duncan H. Mackay ◽  
Stefaan Poedts
Keyword(s):  
Free Field ◽  
Flux Rope ◽  
Decisive Role ◽  
Propagation Speed ◽  
The Sun ◽  
Magnetic Structures ◽  
Mhd Simulations ◽  
Linear Force ◽  
Force Free Field ◽  
Solar Gravity

AbstractCoronal Mass Ejections (CMEs) are one of the most violent phenomena found on the Sun. One model to explain their occurrence is the flux rope ejection model where these magnetic structures firt form in the solar corona then are ejected to produce a CME. We run simulations coupling two models. The Global Non-Linear Force-Free Field (GNLFFF) evolution model to follow the quasi-static formation of a flux rope and MHD simulations for the production of a CME through the loss of equilibrium and ejection of this flux rope in presence of solar gravity and density stratification. Our realistic multi-beta simulations describe the CME following the flux rope ejection and highlight the decisive role played by the gravity stratification on the CME propagation speed.

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