  In this review many of the well known tools for the analysis of Complex
systems are used in order to study the global coupling of the turbulent
convection zone with the solar atmosphere where the magnetic energy is
dissipated explosively. Several well documented observations are not easy to
interpret with the use of Magnetohydrodynamic (MHD) and/or Kinetic numerical
codes. Such observations are: (1) The size distribution of the Active Regions
(AR) on the solar surface, (2) The fractal and multi fractal characteristics of
the observed magnetograms, (3) The Self-Organised characteristics of the
explosive magnetic energy release and (4) the very efficient acceleration of
particles during the flaring periods in the solar corona. We review briefly the
work published the last twenty five years on the above issues and propose
solutions by using methods borrowed from the analysis of complex systems. The
scenario which emerged is as follows: (a) The fully developed turbulence in the
convection zone generates and transports magnetic flux tubes to the solar
surface. Using probabilistic percolation models we were able to reproduce the
size distribution and the fractal properties of the emerged and randomly moving
magnetic flux tubes. (b) Using a Non Linear Force Free (NLFF) magnetic
extrapolation numerical code we can explore how the emerged magnetic flux tubes
interact nonlinearly and form thin and Unstable Current Sheets (UCS) inside the
coronal part of the AR. (c) The fragmentation of the UCS and the redistribution
of the magnetic field locally, when the local current exceeds a Critical
threshold, is a key process which drives avalanches and forms coherent
structures. This local reorganization of the magnetic field, enhances the
energy dissipation and influences the global evolution of the complex magnetic
topology.
