scholarly journals Computing Nonlinear Force-Free Coronal Magnetic Fields in Spherical Geometry

Solar Physics ◽  
2007 ◽  
Vol 240 (2) ◽  
pp. 227-239 ◽  
Author(s):  
T. Wiegelmann
Keyword(s):  
Magnetic Fields ◽  
Spherical Geometry ◽  
Coronal Magnetic Fields ◽  
Nonlinear Force

scholarly journals Nonlinear Force-Free Modeling of Coronal Magnetic Fields. II. Modeling a Filament Arcade and Simulated Chromospheric and Photospheric Vector Fields

Solar Physics ◽  
2008 ◽  
Vol 247 (2) ◽  
pp. 269-299 ◽  
Author(s):  
Thomas R. Metcalf ◽  
Marc L. DeRosa ◽  
Carolus J. Schrijver ◽  
Graham Barnes ◽  
Adriaan A. van Ballegooijen ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Vector Fields ◽  
Coronal Magnetic Fields ◽  
Nonlinear Force

scholarly journals Computing nonlinear force free coronal magnetic fields

2003 ◽  
Vol 10 (4/5) ◽  
pp. 313-322 ◽  
Author(s):  
T. Wiegelmann ◽  
T. Neukirch
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Boundary Conditions ◽  
Random Noise ◽  
Coronal Magnetic Field ◽  
Optimization Method ◽  
Numerical Code ◽  
Coronal Magnetic Fields ◽  
Nonlinear Force ◽  
Free Fields

Abstract. Knowledge of the structure of the coronal magnetic field is important for our understanding of many solar activity phenomena, e.g. flares and CMEs. However, the direct measurement of coronal magnetic fields is not possible with present methods, and therefore the coronal field has to be extrapolated from photospheric measurements. Due to the low plasma beta the coronal magnetic field can usually be assumed to be approximately force free, with electric currents flowing along the magnetic field lines. There are both observational and theoretical reasons which suggest that at least prior to an eruption the coronal magnetic field is in a nonlinear force free state. Unfortunately the computation of nonlinear force free fields is way more difficult than potential or linear force free fields and analytic solutions are not generally available. We discuss several methods which have been proposed to compute nonlinear force free fields and focus particularly on an optimization method which has been suggested recently. We compare the numerical performance of a newly developed numerical code based on the optimization method with the performance of another code based on an MHD relaxation method if both codes are applied to the reconstruction of a semi-analytic nonlinear force-free solution. The optimization method has also been tested for cases where we add random noise to the perfect boundary conditions of the analytic solution, in this way mimicking the more realistic case where the boundary conditions are given by vector magnetogram data. We find that the convergence properties of the optimization method are affected by adding noise to the boundary data and we discuss possibilities to overcome this difficulty.

Nonlinear Force-Free Modeling of Coronal Magnetic Fields Part I: A Quantitative Comparison of Methods

Solar Physics ◽  
2006 ◽  
Vol 235 (1-2) ◽  
pp. 161-190 ◽  
Author(s):  
Carolus J. Schrijver ◽  
Marc L. Derosa ◽  
Thomas R. Metcalf ◽  
Yang Liu ◽  
Jim Mctiernan ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Quantitative Comparison ◽  
Comparison Of Methods ◽  
Coronal Magnetic Fields ◽  
Nonlinear Force

Calculated Coronal Magnetic Fields and Their Comparison with the Coronal Structures as Observed during Five Solar Eclipses

1994 ◽  
Vol 144 ◽  
pp. 559-564
Author(s):  
P. Ambrož ◽  
J. Sýkora
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Magnetic Fields ◽  
Solar Corona ◽  
Coronal Magnetic Field ◽  
Coronal Magnetic Fields ◽  
Solar Eclipses ◽  
Coronal Structures

AbstractWe were successful in observing the solar corona during five solar eclipses (1973-1991). For the eclipse days the coronal magnetic field was calculated by extrapolation from the photosphere. Comparison of the observed and calculated coronal structures is carried out and some peculiarities of this comparison, related to the different phases of the solar cycle, are presented.

scholarly journals Boundary Fitting Problems Associated with Coronal Magnetic Models

1974 ◽  
Vol 57 ◽  
pp. 89-91 ◽  
Author(s):  
Kenneth H. Schatten
Keyword(s):  
Magnetic Fields ◽  
Legendre Polynomial ◽  
Magnetic Monopole ◽  
Polynomial Fit ◽  
Coronal Magnetic Fields ◽  
Boundary Fitting

The calculation of coronal magnetic fields was first suggested by Gold (1958). Altschuler and Newkirk (1969) and Newkirk et al. (1968) used a Legendre polynomial fit to the photospheric observations of magnetic fields whereas Schatten (1968) with Wilcox and Ness (Schatten et al., 1969) use a magnetic monopole fit, first incorporated by Schmidt (1964).

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.

Determining the spatial configurations of the coronal magnetic fields of solar active regions

2013 ◽  
Vol 57 (8) ◽  
pp. 622-635 ◽  
Author(s):  
G. V. Rudenko ◽  
I. I. Mysh’yakov ◽  
S. A. Anfinogentov
Keyword(s):  
Magnetic Fields ◽  
Active Regions ◽  
Coronal Magnetic Fields ◽  
Solar Active Regions ◽  
Spatial Configurations

Thermal condensations in coronal magnetic fields

Solar Physics ◽  
1988 ◽  
Vol 115 (1) ◽  
pp. 61-80 ◽  
Author(s):  
A. Hood ◽  
U. Anzer
Keyword(s):  
Magnetic Fields ◽  
Coronal Magnetic Fields

scholarly journals CURRENT SHEETS FORMATION IN TANGLED CORONAL MAGNETIC FIELDS

2013 ◽  
Vol 773 (1) ◽  
pp. L2 ◽  
Author(s):  
A. F. Rappazzo ◽  
E. N. Parker
Keyword(s):  
Magnetic Fields ◽  
Current Sheets ◽  
Coronal Magnetic Fields
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