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Abstract: Solar active regions are driven dissipative dynamical systems. The turbulentconvection zone forces new magnetic flux tubes to rise above the photosphereand shuffles the magnetic fields which are already above the photosphere. Thedriven 3D active region responds to the driver with the formation of ThinCurrent Sheets in all scales and releases impulsively energy, when specialthresholds are met, on the form of nano-, micro-, flares and large scalecoronal mass ejections. It has been documented that active regions form selfsimilar structures with area Probability Distribution Functions PDF-sfollowing power laws and with fractal dimensions ranging from $1.2-1.7$. Theenergy release on the other hand follows a specific energy distribution law$fE T\sim E T^{-a}$, where $a \sim 1.6-1.8$ and $E T$ is the total energyreleased. A possible explanation for the statistical properties of themagnetogrms and the energy release by the active region is that the magneticfield formation follows rules analogous to \textbf{percolating models}, and the3D magnetic fields above the photosphere reach a \textbf{Self OrganizedCritical SOC state}. The implications of these findings on the accelerationof energetic particles during impulsive phenomena will briefly be outlined.



Author: Loukas Vlahos

Source: https://arxiv.org/



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