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.

scholarly journals Numerical simulations of the CME on 2010 April 8

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.

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.

A Survey of Interplanetary Small Flux Ropes at Mercury

2020 ◽  
Author(s):  
Réka Winslow ◽  
Amy Murphy ◽  
Nathan Schwadron ◽  
Noé Lugaz ◽  
Wenyuan Yu ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Current Sheet ◽  
Heliocentric Distance ◽  
Free Field ◽  
Flux Rope ◽  
Solar Wind Plasma ◽  
The Sun ◽  
Superposed Epoch Analysis ◽  
Flux Ropes

<p>Small flux ropes (SFRs) are interplanetary magnetic flux ropes with durations from a few minutes to a few hours. We have built a comprehensive catalog of SFRs at Mercury using magnetometer data from the orbital phase of the MESSENGER mission (2011-2015). In the absence of solar wind plasma measurements, we developed strict identification criteria for SFRs in the magnetometer observations, including conducting force-free field fits for each flux rope. We identified a total of 48 events that met our strict criteria, with events ranging in duration from 2.5 minutes to 4 hours. Using superposed epoch analysis, we obtained the generic SFR magnetic field profile at Mercury. Due to the large variation in Mercury's heliocentric distance (0.31-0.47 AU), we split the data into two distance bins. We found that the average SFR profile is more symmetric "farther from the Sun", in line with the idea that SFRs form closer to the Sun and undergo a relaxation process in the solar wind. Based on this result, as well as the SFR durations and the magnetic field strength fall-off with heliocentric distance, we infer that the SFRs observed at Mercury are expanding as they propagate with the solar wind. We also determined that the SFR occurrence frequency is nearly four times as high at Mercury as for similarly detected events at 1 AU. Most interestingly, we found two SFR populations in our dataset, one likely generated in a quasi-periodic formation process near the heliospheric current sheet, and the other formed away from the current sheet in isolated events.</p>

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
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