Astronomy and Astrophysics – Astronomy
Scientific paper
May 2003
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003spd....34.0103r&link_type=abstract
American Astronomical Society, SPD meeting #34, #01.03; Bulletin of the American Astronomical Society, Vol. 35, p.805
Astronomy and Astrophysics
Astronomy
Scientific paper
To determine the 3D configuration of solar active regions and to define boundary conditions for MHD codes, we reconstruct the coronal magnetic field from photospheric measurements. For that, we consider the active region in an equilibrium state. Three hypotheses are then often used: the potential field (no electric current), the linear force-free field (the current density is α times the magnetic field, α is a constant), the nonlinear force-free field (α is a function of space). We here compare those three models in terms of connectivity changes and energetics for two different active regions: AR 8151 and AR 8210. AR 8151 shows dramatical changes between these models whereas AR 8210 configuration stays close to the potential field. The structure of the filament and of the sigmoid observed in AR 8151 can only be determined in the nonlinear force-free field: both structures are identified with twisted flux tubes with ˜ 0.5-0.6 turns. Interestingly, the filament is a right-handed structure whereas the sigmoid is left-handed! This work is a part of the Solar MURI project.
Amari Tahar
Canfield Richard C.
Regnier Stéphane
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