Wave-Number Spectra and Intermittency in the Terrestrial Foreshock Region

Y. Narita, K.-H. Glassmeier, R. A. Treumann
2006 Physical Review Letters  
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, ÿ5=3. On the other hand, the fluctuations are highly anisotropic and
more » ... y 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.
doi:10.1103/physrevlett.97.191101 pmid:17155608 fatcat:y4nfjraxp5aodgvt6f63oemtvi