Geometric description of the magnetic field and plasma coupling in the near-Earth stretched tail prior to a substorm

Topological properties of the self-organized magnetic field and plasma turbulence in the near-Earth stretched tail prior to the magnetospheric substorm onset are analyzed. We found that the magnetotail turbulence structures at the late substorm growth phase should be associated with the hierarchical ("singular") geometry; this geometry includes fractal objects, i.e., self-similar "clumpy" structures with "voids" present on many scales. The fractal description of the self-organized magnetic field and electric current coupling in the tail has led us to the idea of the "geometric" formulation of the basic physical processes in the tail; this formulation deals with certain topological "codes" (i.e., algebraic relations between the principal geometric parameters) and is an alternative of the more traditional approach based on the direct analysis of the corresponding nonlinear differential equations. A "topological scenario" for the substorm onset is further proposed, and the relevant "codes" characterizing the microscopic structural properties of the turbulence are obtained. The behavior of the Fourier energy density spectra of the magnetic field and cross-tail electric current fluctuations is discussed. The results of the numerical modeling of the turbulence at the late growth phase are given. (C) 2001 Elsevier Science Ltd. All rights reserved.