Universality of Solar-Wind Turbulent Spectrum from MHD to Electron Scales

Olga Alexandrova , J. Saur , C. Lacombe , Anne Mangeney , J. Mitchell , S. J. Schwartz , Patrick Robert (1)

1 LPP - Laboratoire de Physique des Plasmas

To investigate the universality of magnetic turbulence in space plasmas, we analyze seven time periods in the free solar wind under different plasma conditions. Three instruments on Cluster spacecraft operating in different frequency ranges give us the possibility to resolve spectra up to 300 Hz. We show that the spectra form a quasiuniversal spectrum following the Kolmogorov’s law ∼k−5/3 at MHD scales, a ∼k−2.8 power law at ion scales, and an exponential ∼exp[−√kρe] at scales kρe∼[0.1,1], where ρe is the electron gyroradius. This is the first observation of an exponential magnetic spectrum in space plasmas that may indicate the onset of dissipation. We distinguish for the first time between the role of different spatial kinetic plasma scales and show that the electron Larmor radius plays the role of a dissipation scale in space plasma turbulence.

Domaines: Astrophysique [astro-ph]; Physique des plasmas [physics.plasm-ph]

Olga Alexandrova, J. Saur, C. Lacombe, Anne Mangeney, J. Mitchell, et al.. Universality of Solar-Wind Turbulent Spectrum from MHD to Electron Scales. Physical Review Letters, 2009, 103, pp.165003. ⟨10.1103/PhysRevLett.103.165003⟩. ⟨hal-01553809⟩