Bootstrapping the coronal magnetic field with STEREO: I. Unipolar Potential Field Modeling
Markus J. Aschwanden Submitted: 2010-04-27 16:25
We investigate the recently quantified misalignment of α mis
approx 20°-40° between the 3-D geometry of
stereoscopically triangulated coronal loops observed with STEREO/EUVI
(in four active regions)
and theoretical (potential or nonlinear force-free) magnetic field models
extrapolated from photospheric magnetograms. We develop an efficient method
of bootstrapping the coronal magnetic field by forward-fitting a
parameterized potential field model to the STEREO-observed loops.
The potential field model consists of a number of unipolar magnetic
charges that are parameterized by decomposing a photospheric magnetogram
from MDI. The forward-fitting method yields a best-fit magnetic field model
with a reduced misalignment of α PF approx 13°-20°.
We evaluate also stereoscopic measurement errors and find a contribution
of α SEapprox 7°-12°, which constrains the residual
misalignment to α NP α PF α SEapprox 5°
-9°, which is likely due to the nonpotentiality of the active regions.
The residual misalignment angle α NP of the potential field due
to nonpotentiality is found to correlate with the soft X-ray flux of
the active region, which implies a relationship between electric currents
and plasma heating.
Authors: Markus J. Aschwanden and Anne W. Sandman
Publication Status: Astronomical Journal 140, 723-734, (2010, Sept issue)
Last Modified: 2010-08-06 12:38