Nature of the 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. Focus is put on the magnetic energy spectra computed in the frequency range of ∼[10-4, 1]Hz. A set of 42 time intervals in the magnetosheath were analyzed, and three main results that contrast with known features of solar wind turbulence are reported. (1) The magnetic energy spectra showed a ∼f-1 scaling at MHD scales followed by an scaling at sub-ion scales without forming the so-called inertial range. (2) The magnetic compressibility and the cross-correlation between the parallel component of the magnetic field and density fluctuations indicate the dominance of the compressible magnetosonic slow-like modes at MHD scales rather than the Alfvén mode. (3) Higher-order statistics revealed a monofractal (multifractal) behavior of the turbulent flow downstream of a quasi-perpendicular (quasi-parallel) shock at sub-ion scales. Implications of these results on theoretical modeling of space plasma turbulence are discussed.