Preprocessing of Vector Magnetograph Data for a Nonlinear Force-Free Magnetic Field Reconstruction

By T. Wiegelmann, B. Inhester, T. Sakurai. 2006

367 citations recorded by the source corpus.

Knowledge regarding the coronal magnetic field is important for the understanding of many phenomena, like flares and coronal mass ejections. Because of the low plasma beta in the solar corona, the coronal magnetic field is often assumed to be force-free and we use photospheric vector magnetograph data to extrapolate the magnetic field into the corona with the help of a nonlinear force-free optimization code. Unfortunately, the measurements of the photospheric magnetic field contain inconsistencies and noise. In particular, the transversal components (say Bx and By) of current vector magnetographs have their uncertainties. Furthermore, the magnetic field in the photosphere is not necessarily force free and often not consistent with the assumption of a force-free field above the magnetogram. We develop a preprocessing procedure to drive the observed non–force-free data towards suitable boundary conditions for a force-free extrapolation. As a result, we get a data set which is as close as possible to the measured data and consistent with the force-free assumption.

Subfields: Astronomy and Astrophysics, Molecular Biology, Oceanography

View Paper: https://www.semanticscholar.org/paper/ce12975e8ec4995ad1a2d56bf47caf0293d851e0

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

In Molecular Biology

In Oceanography

Citations in the corpus

COEXISTING FLUX ROPE AND DIPPED ARCADE SECTIONS ALONG ONE SOLAR FILAMENT (2010, methodology): “…Kliem (2003), it has been recently shown that NLFFF extrapolation codes are capable of reconstructing significantly twisted flux ropes, as well as topological features of active region magnetic fields, with a high degree of accuracy (Valori et al. 2005; Wiegelmann et al. 2006a; Valori et al. 2010).”
EVOLUTION OF MAGNETIC FIELD AND ENERGY IN A MAJOR ERUPTIVE ACTIVE REGION BASED ON SDO/HMI OBSERVATION (2011, methodology): “A preprocessing procedure removes most of the net force and torque from the data so the boundary can be more consistent with the force-free assumption (Wiegelmann et al. 2006).”
WHY IS THE GREAT SOLAR ACTIVE REGION 12192 FLARE-RICH BUT CME-POOR? (2015, methodology): “We study the coronal field by extrapolating a nonlinear force-free field (NLFFF; Wiegelmann 2004; Wiegelmann et al. 2006) and a potential field (PF; e.g., Sakurai 1989) from each vector magnetogram (Sun et al. 2012).”
A CRITICAL ASSESSMENT OF NONLINEAR FORCE-FREE FIELD MODELING OF THE SOLAR CORONA FOR ACTIVE REGION 10953 (2009, methodology): “The third variant was to use the method of preprocessing described in Fuhrmann et al. (2007), the goals of which are the same as the Wiegelmann et al. (2006), but which uses a simulated annealing numerical scheme to find the optimal B|z0 field.”
The Helioseismic and Magnetic Imager (HMI) Investigation for the Solar Dynamics Observatory (SDO) (2012, methodology): “The optimization code for inference of non-linear force-free coronal magnetic fields is based on work by Wiegelmann (2004) and Wiegelmann, Inhester, and Sakurai (2006).”
Solar Force-free Magnetic Fields (2012, methodology): “These identified loops can then be directly compared with the projections of the magnetic field lines, e.g., by computing the area spanned between the loop and the field line as defined in Wiegelmann et al. (2006b).”
Nonlinear Force-free Field Modeling of a Solar Active Region around the Time of a Major Flare and Coronal Mass Ejection (2007, methodology): “The preprocessing is performed with a method devised by Metcalf et al. (2008) which leaves Bz unchanged and one by Wiegelmann et al. (2006) which allows all field components to change.”
How Should One Optimize Nonlinear Force-Free Coronal Magnetic Field Extrapolations from SDO/HMI Vector Magnetograms? (2012, methodology): “(Wiegelmann, Inhester, and Sakurai, 2006) introduced three dimensionless parameters, the flux balance flux, net force balance force and net torque balance torque: flux = ∫ S Bz∫ S |Bz| force = | ∫ S BxBz|+ | ∫ S ByBz|+ | ∫ S (B2x +B 2 y)−B2z |∫ S (B2x +B 2 y +B 2 z ) torque = | ∫ S x((B2x +B 2…”
Nonlinear Force-Free Modeling of Coronal Magnetic Fields. II. Modeling a Filament Arcade and Simulated Chromospheric and Photospheric Vector Fields (2008, methodology): “To do so, we minimize a 2D functional, similar to that from Wiegelmann, Inhester, and Sakurai (2006): L = μ1L1 + μ2L2 + μ3xL3x + μ3yL3y + μ3zL3z + μ4L4, (7) where L1 = [(∑ p BxBz )2 + (∑ p ByBz )2 + (∑ p B2z − B2x − B2y )2] , L2 = [(∑ p x ( B2z − B2x − B2y ))2 + (∑ p y ( B2z − B2x − B2y ))2 +…”