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Nonlinear Processes in Geophysics An interactive open-access journal of the European Geosciences Union
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Volume 8, issue 3
Nonlin. Processes Geophys., 8, 175–180, 2001
https://doi.org/10.5194/npg-8-175-2001
© Author(s) 2001. This work is licensed under
the Creative Commons Attribution-NonCommercial-ShareAlike 2.5 License.

Special issue: Theory and simulation of Solar System Plasmas, No. 2

Nonlin. Processes Geophys., 8, 175–180, 2001
https://doi.org/10.5194/npg-8-175-2001
© Author(s) 2001. This work is licensed under
the Creative Commons Attribution-NonCommercial-ShareAlike 2.5 License.

  30 Jun 2001

30 Jun 2001

An example of resonances, coherent structures and topological phase transitions - the origin of the low frequency broadband spectrum in the auroral zone

T. Chang T. Chang
  • Center for Space Research, Massachusetts Institute of Technology Cambridge, MA 02139, USA

Abstract. We consider the phenomena of intermittent turbulence in magnetized space plasmas from the point of view of topological phase transitions involving the merging and interactions of anisotropic coherent structures. The stochastic behaviour of these coherent plasma structures can undergo complex changes as the dynamic system evolves, similar to those commonly observed in (first and second order) equilibrium phase transitions. When conditions are favourable, such topological entities can evolve into a state of forced and/or self-organized criticality (FSOC). As an example, we apply these ideas to the understanding of the origin of the commonly observed broadband power-law low frequency electric field spectral densities and the characteristic filamentary current structures in the auroral zone. The broadband turbulence can provide efficient resonant energization of the ionospheric oxygen ions.

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