Résumé du preprint DAPNIA-07-151

Multifractal properties of evolving active regions
P. A. Conlon, P. T.Gallagher, R. T. J. McAteer, J. Ireland, C. A. Young, P. Kestener, R. J. Hewett, K. Maguire
Magnetohydrodynamic turbulence is thought to be responsible for producing complex, multiscale field distributions in solar active regions. Here we explore the multiscale
properties of a number of evolving active regions using magnetograms from the Michelson
Doppler Imager (MDI) on the Solar and Heliospheric Observatory (SOHO). The multifrac-
tal spectrum was obtained using a modified box-counting method to study the relationship
between magnetic field multifractality and region evolution and activity. The initial emer-
gence of each active region was found to be accompanied by characteristic changes in the
multfractal spectrum. Specifically, the range of multifractal structures (Ddiv ) was found
to increase during emergence, as was their significance or support (Cdev ). Following this, a
decrease in the range in multfractal structures occurred as the regions evolved to become
large-scale, coherent structures. From the small sample considered, evidence was found for
a direct relationship between the multifractal properties of the flaring regions and their
flaring rate.


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