On the nature of MHD and kinetic scale turbulence in the magnetosheath of Saturn: Cassini observations

Abstract : Low frequency turbulence in Saturn’s magnetosheath is investigated using in-situ measurements of the Cassini spacecraft. We focus on the magnetic en- ergy spectra computed in the frequency range ∼ [10−4 , 1]Hz. Three main results are reported: 1) The magnetic energy spectra showed a ∼ f−1 scaling at MHD scales followed by an ∼ f−2.6 scaling at the sub-ion scales without forming the so-called inertial range, breaking the universality of the Kolmogorov spectrum in the magnetosheath; 2) The magnetic com- pressibility and the cross-correlation between the par- allel component of the magnetic field and density fluctuations C(δn, δB||) indicate the dominance of the compressible magnetosonic slow modes at MHD scales rather than the Alfvén mode [3] ; 3) Higher order statistics revealed a monofractal (resp. multi- fractal) behaviour of the turbulent flow behind a quasi- perpendicular (resp. quasi-parallel) shock at the sub- ion scales.