Three-Dimensional Magnetic and Velocity Structures of Active Region 12673

2020 ◽  
Author(s):  
Haimin Wang
Keyword(s):  
Active Region ◽  
Magnetic Fields ◽  
Thermal Structure ◽  
Transverse Velocity ◽  
Free Field ◽  
Three Dimensional ◽  
Velocity Fields ◽  
Height Range ◽  
Cycle 24 ◽  
Force Free Field

<p>We study the Solar Active Region (AR) 12673 in September 2017, which is the most flare productive AR in the solar cycle 24.  Observations from Goode Solar Telescope (GST) show the strong photospheric magnetic fields (nearly 6000 G) in polarity  inversion line (PIL) and apparent photospheric twist on September 6,  the day of X9.3 flare. Corresponding to the strong twist,   upflows are observed to last one day  at the center part of that section of PIL;  down flows are observed in two ends.  Transverse velocity fields are derived from flow tracking.   Both Non-Linear Force-Free Field (NLFFF) and Non-Force-Free Field (NFFF) extrapolations are carried out and compared to trace 3-D magnetic fields in corona. Combining with EOVSA, coronal magnetic fields between 1000 and 2000 gauss are found above the flaring PIL at the height range between 8 and 4Mm, outlining the structure of a fluxrope with sheared arcade.  The above magnetic and velocity fields, as well as thermal structure of corona, provide initial condition for further data-driven MHD simulation.</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 Study of magnetic field topology of active region 12192 using an extrapolated non-force-free magnetic field

2018 ◽  
Vol 13 (S340) ◽  
pp. 81-82
Author(s):  
A. Prasad ◽  
R. Bhattacharyya ◽  
Q. Hu ◽  
S. S. Nayak ◽  
Sanjay Kumar
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Free Field ◽  
Coronal Magnetic Field ◽  
Solar Photosphere ◽  
Magnetic Field Topology ◽  
Cycle 24 ◽  
Magnetic Null ◽  
The Magnetic Field ◽  
Force Free Field

AbstractThe solar active region (AR) 12192 was one of the most flare productive region of solar cycle 24, which produced many X-class flares; the most energetic being an X3.1 flare on October 24, 2014 at 21:10 UT. Customarily, such events are believed to be triggered by magnetic reconnection in coronal magnetic fields. Here we use the vector magnetograms from solar photosphere, obtained from Heliospheric Magnetic Imager (HMI) to investigate the magnetic field topology prior to the X3.1 event, and ascertain the conditions that might have caused the flare. To infer the coronal magnetic field, a novel non-force-free field (NFFF) extrapolation technique of the photospheric field is used, which suitably mimics the Lorentz forces present in the photospheric plasma. We also highlight the presence of magnetic null points and quasi-separatrix layers (QSLs) in the magnetic field topology, which are preferred sites for magnetic reconnections and discuss the probable reconnection scenarios.

Preprocessing of magnetograms for magnetohydrostatic extrapolations

2021 ◽  
Author(s):  
Xiaoshuai Zhu ◽  
Thomas Wiegelmann ◽  
Bernd Inhester
Keyword(s):  
Active Region ◽  
Magnetic Fields ◽  
Magnetic Energy ◽  
Free Field ◽  
Original Data ◽  
Boundary Integral ◽  
New Criteria ◽  
Force Free Field ◽  
Surface Integrals

<p>Magnetohydrostatic (MHS) extrapolations are developed to model 3D magnetic fields and plasma structures in the solar low atmosphere by using measured vector magnetic fields on the photosphere. However, the photospheric magnetogram may be inconsistent with the MHS assumption. By applying Gauss‘ theorem to an isolated active region, we obtain a set of surface integrals of the magnetogram as criteria for a MHS system. The integrals are a subset of Aly’s criteria for a force-free field (FFF). Based on the new criteria, we preprocess the magnetogram to make it more consistent with the MHS assumption and, at the same time, close to the original data. As a byproduct, we also find the boundary integral that is used to compute the energy of a FFF usually underestimates the magnetic energy of an active region.</p>

scholarly journals Nonlinear force-free modeling of magnetic fields in flare-productive active regions

2015 ◽  
Vol 11 (S320) ◽  
pp. 167-174
Author(s):  
M. S. Wheatland ◽  
S. A. Gilchrist
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Boundary Data ◽  
Numerical Solutions ◽  
Free Field ◽  
Active Regions ◽  
Coronal Magnetic Field ◽  
Nonlinear Force ◽  
The Magnetic Field ◽  
Force Free Field

AbstractWe review nonlinear force-free field (NLFFF) modeling of magnetic fields in active regions. The NLFFF model (in which the electric current density is parallel to the magnetic field) is often adopted to describe the coronal magnetic field, and numerical solutions to the model are constructed based on photospheric vector magnetogram boundary data. Comparative tests of NLFFF codes on sets of boundary data have revealed significant problems, in particular associated with the inconsistency of the model and the data. Nevertheless NLFFF modeling is often applied, in particular to flare-productive active regions. We examine the results, and discuss their reliability.

scholarly journals Quasi–Static Evolution of Force–Free Magnetic Fields and a Model for Two–Ribbon Solar Flares

1985 ◽  
Vol 107 ◽  
pp. 221-224
Author(s):  
J. J. Aly
Keyword(s):  
Magnetic Fields ◽  
Solar Flares ◽  
Free Field ◽  
Qualitative Theory ◽  
Force Free Field ◽  
Open Configuration

We show that a sheared 2–D force–free field can evolve in a quasi–static way towards an open configuration, and apply this result to a qualitative theory of two–ribbon solar flares.

scholarly journals Nonlinear Force‐free Field Modeling of a Solar Active Region around the Time of a Major Flare and Coronal Mass Ejection

2008 ◽  
Vol 675 (2) ◽  
pp. 1637-1644 ◽  
Author(s):  
C. J. Schrijver ◽  
M. L. DeRosa ◽  
T. Metcalf ◽  
G. Barnes ◽  
B. Lites ◽  
...  
Keyword(s):  
Active Region ◽  
Coronal Mass Ejection ◽  
Free Field ◽  
Solar Active Region ◽  
Field Modeling ◽  
Major Flare ◽  
Nonlinear Force ◽  
Mass Ejection ◽  
Force Free Field
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