Magnetohydrodynamic (MHD) turbulence in the solar wind is observed to show the
spectral behavior of classical Kolmogorov fluid turbulence over an inertial subrange
and departures from this at short wavelengths, where energy should be dissipated.
Here we present the first measurements of the electric field fluctuation spectrum over
the inertial and dissipative wavenumber ranges in a eta gtrsim 1 plasma.
The k-5/3 inertial subrange is
observed and agrees strikingly with the magnetic fluctuation spectrum; the wave phase speed
in this regime is shown to be consistent with the Alfvén speed. At smaller wavelengths
ho_i geq 1 the electric spectrum is softer and is consistent with the expected
dispersion relation of short-wavelength kinetic Alfvén waves. Kinetic Alfvén waves
damp on the solar wind ions and electrons and may act to isotropize them. This effect may explain the
fluid-like nature of the solar wind.
Authors: S. D. Bale, P. J. Kellogg, F. S. Mozer, T. S. Horbury, and H. Reme
Publication Status: submitted
Last Modified: 2005-03-12 13:12