title: Wave-number spectra and intermittency in the terrestrial foreshock region.
abstract: Wave-number spectra of magnetic field fluctuations are directly determined in the terrestrial foreshock region (upstream of a quasiparallel collisionless shock wave) using four-point Cluster spacecraft measurements. The spectral curve is characterized by three ranges reminiscent of turbulence: energy injection, inertial, and dissipation range. The spectral index for the inertial range spectrum is close to Kolmogorov's slope, -5/3. On the other hand, the fluctuations are highly anisotropic and intermittent perpendicular to the mean magnetic field direction. These results suggest that the foreshock is in a weakly turbulent and intermittent state in which parallel propagating Alfvén waves interact with one another, resulting in the phase coherence or the intermittency.
authors.affiliation: Institute of Geophysics and Extraterrestrial Physics, Mendelssohnstrasse 3, D-38106 Braunschweig, Germany. y.narita@tu-bs.de
authors.forename: Y
authors.initials: Y
authors.lastname: Narita
authors.forename: K-H
authors.initials: KH
authors.lastname: Glassmeier
authors.forename: R A
authors.initials: RA
authors.lastname: Treumann