Anisotropy evolution of magnetic field fluctuation through the bow shock

Y. Narita [1] and K.-H. Glassmeier [1,2]

[1] Institut fuer Geophysik und extraterrestrische Physik, 
Technische Universitaet Braunschweig, Mendelssohnstr. 3, 
D-38116 Braunschweig, Germany
[2] Max-Planck-Institut fuer Sonnensystemforschung, 
Max-Planck-Str. 2, D-37191 Katlenburg-Lindau, Germany

We investigate wave vector anisotropies of magnetic field
fluctuations using Cluster magnetometer data and the
wave telescope technique. The energy distributions are
determined in various regions from the solar wind to the magnetosheath
and the cusp region across the bow shock, which allows us to study
how wave vector anisotropies of turbulent magnetic field 
fluctuations evolve as the solar wind encounters the
terrestrial bow shock and the magnetosphere. While fluctuations 
in the solar wind, the magnetosheath, and the magnetospheric cusp 
regions are characterized by the perpendicular wave vector geometry 
with respect to the mean magnetic field direction, that in the foreshock region 
is characterized by the parallel wave vector geometry. These transitions
are discussed from the viewpoint of linear instabilities and nonlinear processes.