Astronomy and Astrophysics – Astronomy
Scientific paper
May 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007aas...210.9105l&link_type=abstract
American Astronomical Society Meeting 210, #91.05; Bulletin of the American Astronomical Society, Vol. 39, p.204
Astronomy and Astrophysics
Astronomy
Scientific paper
The magnetic field measurements in the corona above two quiet, close active regions NOAA 10581 and 10582 at the solar west limb were taken by the new coronagraph SOLARC installed on Haleakala. Spatially resolved measurements of line-of-sight magnetic field strength and transverse magnetic field direction of the solar corona were obtained at the wavelength of IR 1074.7 nm. In the two-dimensional coronal magnetogram made from the circular polarization, the observations showed a magnetic neutral line at a height of about 0.16 solar radii above the solar limb. Signatures of the the van Vleck effect were also shown from the linear polarization measurements. These new coronal data, for the first time, direct observational tests for theoretical coronal magnetic field models. In this paper, we present a study comparing the observed coronal magnetic field structures with the theoretical results derived from the global potential field model. One important conclusion in the study is that the SOLARC observations should reveal the local coronal structures above strong photospheric field regions, since both the observed linear and circular polarization signals are found to have a best consistence with the calculated results for a 100 Mm-thick coronal region along the line of sight above the sunspot in NOAA 10582. The usefulness and limitations of the potential field extrapolation and various linear and non-linear force-free field extrapolation methods, as well as directions for a more sophisticated modelling effort involving MHD simulations and forward modeling of the polarization signals that take full account of atomic polarization and radiative transfer effects will be further studied and discussed.
Lin Hainan
Liu Yu
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