HR: 09:45h
AN: NG41A-08    [Abstracts]
TI: Magnetic turbulence spectra in the shock upstream solar wind
AU: * Narita, Y
EM: y.narita@tu-bs.de
AF: Institut fuer Geophysik und extraterrestrische Physik, Mendelssohnstr. 3, Braunschweig, 38106 Germany
AU: Glassmeier, K
EM: kh.glassmeier@tu-bs.de
AF: Institut fuer Geophysik und extraterrestrische Physik, Mendelssohnstr. 3, Braunschweig, 38106 Germany
AU: Treumann, R
EM: art@mpe.mpg.de
AF: Max-Planck-Institut fuer extraterrestrische Physk, Giessenbachstr., Garching, 85748 Germany
AB: Since Kolmogorov in 1941 postulated isotropic energy cascade process for hydrodynamic turbulence, it has been discussed whether such turbulence can also be found in plasmas, yet we do not have a direct evidence for it, as one needs to measure scales and their associated energies in space. Using Cluster four-spacecraft, however, it has become possible to measure scales, and we present the first direct determination of magnetic turbulence spectra and their directional dependence in the collisionless high-beta solar wind plasma upstream of Earth's bow shock (foreshock) without assuming that temporal variations represent only spatial variations. The spectra exhibit three ranges: the injection range identified with the wave coupling region between two different wave modes, the inertial range, and the dissipation range. We suggest that the shock upstream turbulence is about isotropic and close to Kolmogorov rather than Kraichnan model, and that magnetic viscosity dominates parallel to the background magnetic field at the ion inertial length and perpendicular at the thermal ion gyroradius.
DE: 2149 MHD waves and turbulence (2752, 6050, 7836)
SC: Nonlinear Geophysics [NG]
MN: Fall Meeting 2005