Astronomy and Astrophysics – Astrophysics
Scientific paper
Dec 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufmsh53b..02g&link_type=abstract
American Geophysical Union, Fall Meeting 2010, abstract #SH53B-02
Astronomy and Astrophysics
Astrophysics
[7509] Solar Physics, Astrophysics, And Astronomy / Corona, [7519] Solar Physics, Astrophysics, And Astronomy / Flares, [7524] Solar Physics, Astrophysics, And Astronomy / Magnetic Fields
Scientific paper
Active region AR 11029 was a small but highly active sunspot region that produced over 70 GOES soft X-ray flares during its transit of the disk in late October 2009, during a period of deep solar minimum. The flares appear to show a departure from the well known flare power-law frequency-size distribution. Specifically, too few GOES C class and no M class flares were observed by comparison with a simple power-law distribution (Wheatland 2010). This was conjectured to be due to the region having insufficient magnetic energy to power large events (Wheatland 2010). We perform nonlinear force-free modeling of the coronal magnetic field of the region on 24, 25 and 26 October using three photospheric magnetograms provided by the SOLIS vector spectromagnetograph. We find the free magnetic energy of the region is ≤ 1030 ergs which is consistent with the region having insufficient energy to produce large flares. A recently developed self-consistency procedure (Wheatland and Régnier 2009) is applied to overcome the incompatibility between the force-free model and the forced photospheric data. Force-free model of the coronal magnetic field (black field lines) of AR 11029 on 24 October superimposed on SOLIS magnetogram data. The magnetogram shows the line-of-sight magnetic field on the photosphere. Positive polarity regions are colored blue and negative polarity regions are colored red.
Gilchrist S. A.
Wheatland Michael S.
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