title: Observational Test for a Random Sweeping Model in Solar Wind Turbulence.
abstract: Evidence of frequency broadening at ion kinetic scales due to large-scale eddies and waves is found in solar wind turbulence by a test for a random sweeping model using the magnetic energy spectrum in the frequency vs wave number domain in the comoving frame of the flow obtained from multispacecraft observations. The statistical analysis of the frequency vs wave number spectra without using Taylor's hypothesis shows Gaussian frequency broadening around nearly zero frequencies that increases for larger wave numbers and non-Gaussian tails at higher frequencies. Comparison of the observed frequency broadening with a random sweeping model derived from hydrodynamic turbulence reveals similarities with respect to the Gaussian shape. The standard deviation of the broadening scales with ∼k^{1.6±0.2} and differs from the hydrodynamic turbulence model that predicts ∼k^{2/3}. We interpret this stronger increasing broadening as a consequence of the more diverse large scale structures (eddies and waves) in plasma turbulence and the accompanied more complex sweeping. Consequently, an identification and association of waves with normal modes based on their dispersion relation only, in particular at ion kinetic scales and below, is not possible in solar wind turbulence.
authors.affiliation: Institut für theoretische Physik, Technische Universität Braunschweig, Mendelssohnstraße 3, D-38106 Braunschweig, Germany.|Institut für Geophysik und extraterrestrische Physik, Technische Universität Braunschweig, Mendelssohnstraße 3, D-38106 Braunschweig, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Perschke
authors.affiliation: Institut für Geophysik und extraterrestrische Physik, Technische Universität Braunschweig, Mendelssohnstraße 3, D-38106 Braunschweig, Germany.|Space Research Institute, Austrian Academy of Sciences, Schmiedlstraße 6, A-8042 Graz, Austria.
authors.forename: Y
authors.initials: Y
authors.lastname: Narita
authors.affiliation: Institut für theoretische Physik, Technische Universität Braunschweig, Mendelssohnstraße 3, D-38106 Braunschweig, Germany.|Deutsches Zentrum für Luft- und Raumfahrt, Institut für Planetenforschung, Rutherfordstraße 2, D-12489 Berlin, Germany.
authors.forename: U
authors.initials: U
authors.lastname: Motschmann
authors.affiliation: Institut für Geophysik und extraterrestrische Physik, Technische Universität Braunschweig, Mendelssohnstraße 3, D-38106 Braunschweig, Germany.|Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, D-37077 Göttingen, Germany.
authors.forename: K H
authors.initials: KH
authors.lastname: Glassmeier