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Photospheric and Coronal Currents in Solar Active Regions View all abstracts by submitter

Richard Canfield   Submitted: 2002-12-13 11:55

Using photospheric line of sight magnetograms from the National SolarObservatory/Kitt Peak and coronal X-ray images from the Yohkoh Soft X-ray Telescope, we have determined the value of the constant α of the linear force-free-field model that gives the best visual fit to the most distinct coronal X-ray features of 34 active regions. We find that such features in most of these regions are well represented by a linear force-free-field model with a single coronal α value. Only 11% clearly require more than one coronal α value. For 24 well-developed and flare-productive active regions, vector magnetograms are available from the Haleakala Stokes Polarimeter at Mees Solar Observatory. For each of them we determine the single best-fit value of α in the photosphere by three quite different methods, and show that these methods give consistent values. By combining this dataset with that of NSO and SXT, we are able to compare for the first time quantitatively and statistically the observed values of α in the photosphere and corona of these regions. We find that the distribution of photospheric and coronal α values is fully consistent with the hypothesis that the overall twist density of the magnetic fields of flare-productive mature active regions, as measured by the linear force-free field parameter α is the same in the photosphere and the corona. We therefore conclude that the electric currents that create the non-potential structure of such solar coronal active regions are of sub-photospheric origin and pass without significant modification through the photosphere.

Authors: Burnette, A.B., Canfield, R.C, Pevtsov, A.A.
Projects: None

Publication Status: ApJ, published
Last Modified: 2004-04-26 10:35
Go to main E-Print page  What is the role of the kink instability in solar eruptions?   Astrophysics 2002 (Section 2: Solar Physics)  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

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