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Sigmoidal Active Region on the Sun: Comparison of a Magnetohydrodynamical Simulation and a Non-Linear Force-Free Field Model
 

Summary: Sigmoidal Active Region on the Sun: Comparison of a
Magnetohydrodynamical Simulation and a Non-Linear Force-Free Field Model
savcheva@bu.edu
A. Savcheva1,2, E. Pariat3, A. van Ballegooijen1, G. Aulanier3 & E. DeLuca1
1Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA;
2Astronomy Department, Boston University, 725 Commonwealth ave., Boston, MA02215, USA;
3LESIA, Observatoire de Paris, CNRS, UPMC, Universit´e Paris Diderot, 92190 Meudon, France
savcheva@bu.edu
ABSTRACT
In this paper we show that when accurate non-linear force free field (NLFFF) models
are analyzed together with high resolution magnetohydrodynamic (MHD) simulations,
we can determine the physical causes for the CME eruption on 12-Feb-2007. We compare
the geometrical and topological properties of the three-dimensional magnetic fields given
by both methods in their pre-eruptive phases. We arrive at a consistent picture for the
evolution and eruption of the sigmoid. Both the MHD simulation and the observed
magnetic field evolution show that flux cancellation plays an important role in building
the flux rope. We compute the squashing factor, Q, in different horizontal maps in
the domains. The main shape of the quasi-separatrix layers (QSLs), are very similar
between the NLFFF and MHD models. The main QSLs lie on the edge of the flux
rope. While the QSLs in the NLFFF model are more complex due to the intrinsic large

  

Source: Aulanier, Guillaume - Observatoire de Paris

 

Collections: Physics