title: Three dimensional anisotropic κ spectra of turbulence at subproton scales in the solar wind.
abstract: We show the first three dimensional (3D) dispersion relations and k spectra of magnetic turbulence in the solar wind at subproton scales. We used the Cluster data with short separations and applied the k-filtering technique to the frequency range where the transition to subproton scales occurs. We show that the cascade is carried by highly oblique kinetic Alfvén waves with ω(plas) ≤ 0.1ω(ci) down to k(⊥) ρ(i)∼2. Each k spectrum in the direction perpendicular to B0 shows two scaling ranges separated by a breakpoint (in the interval [0.4,1]k(⊥)ρ(i): a Kolmogorov scaling k(⊥)⁻¹ⁱ⁷ followed by a steeper scaling ∼k(⊥)⁻⁴ⁱ⁵. We conjecture that the turbulence undergoes a transition range, where part of the energy is dissipated into proton heating via Landau damping and the remaining energy cascades down to electron scales where electron Landau damping may predominate.
authors.affiliation: Laboratoire de Physique des Plasmas, CNRS-Ecole Polytechnique-UPMC, Observatoire de Saint-Maur, 4 avenue de Neptune, 94107 Saint-Maur-des-Fossés, France. fouad.sahraoui@lpp.polytechnique.fr
authors.forename: F
authors.initials: F
authors.lastname: Sahraoui
authors.forename: M L
authors.initials: ML
authors.lastname: Goldstein
authors.forename: G
authors.initials: G
authors.lastname: Belmont
authors.forename: P
authors.initials: P
authors.lastname: Canu
authors.forename: L
authors.initials: L
authors.lastname: Rezeau