Self-organized branching of magnetotail current systems near the percolation threshold

This paper advocates an application of the fractal topology formalism to an analysis of the magnetotail current systems. Our main attention is concent rated on the magnetotail regions with the considerably stretched background magnetic field; such conditions can be the case in the distant tail, as we ll as in the near-Earth tail at the late substorm growth phase. Structural properties of the current system at the self-organized (quasi)stationary st ates are analyzed in relationship with the universal fractal geometry of th e percolating fractal sets near the critical threshold. We found that the v iolation of the criticality character leads to the topological phase transi tion in the system; this transition has features of a structural catastroph e and is associated with the magnetospheric substorm onset. A comparison wi th various observational studies is given, and the possible directions of t he future research are outlined.