Magnetic turbulence in and around the Earth's magnetosphere

Magnetic turbulence is found in most space plas- mas, including the geospace environment. Recent spacecraft observations of magnetic turbulence in the ion foreshock, in the magnetosheath, in the polar cusp regions, and in the magnetotail will be reviewed. Turbulence features like the fluctuation level, the spectral power law index, the turbu- lence anisotropy and intermittency, and the turbulence driver will be addressed. The influence of such a turbulence on the plasma transport and dynamics will be described, also using the results of numerical simulations. space plasmas, which then evolve into a power-law spectrum thanks to nonlinear interactions. Magnetic turbulence due to both phenomenologies is observed in and around the Earth's magnetosphere. Such a turbulence can be due either to veloc- ity shear instabilities in the magnetosheath, or to magnetic re- connection at magnetic field reversals like the magnetopause and the magnetotail, or to kinetic instabilities due to parti- cle beams and to the anisotropic distribution functions in the bow shock and in the magnetotail. Many spacecraft have explored the near Earth space, yield- ing a rich set of magnetic field observations (e.g. Zimbardo, 2006). The International Heliophysical Year gives the op- portunity to study these data in a coordinated, comparative way, and here we point out that similar analysis techniques can be used for different datasets. The observations point out the importance of the underlying nonlinear dynamics, but the many behaviours of plasmas and magnetofluids show that further studies are needed. Here we describe some stimulat- ing, and often puzzling, observations, and indicate how the understanding of some problems can be advanced by the use of numerical simulations.