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 turb ulence in the near-Earth stretched tail prior to the magnetospheric substor m onset are analyzed. We found that the magnetotail turbulence structures a t 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 fracta l description of the self-organized magnetic field and electric current cou pling 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 certa in topological "codes" (i.e., algebraic relations between the principal geo metric parameters) and is an alternative of the more traditional approach b ased on the direct analysis of the corresponding nonlinear differential equ ations. A "topological scenario" for the substorm onset is further proposed , and the relevant "codes" characterizing the microscopic structural proper ties of the turbulence are obtained. The behavior of the Fourier energy den sity spectra of the magnetic field and cross-tail electric current fluctuat ions is discussed. The results of the numerical modeling of the turbulence at the late growth phase are given. (C) 2001 Elsevier Science Ltd. All righ ts reserved.