Magnetic field turbulence in the solar wind at sub-ion scales: in situ observations and numerical simulations

摘要: We investigate the transition of solar wind turbulent cascade from MHD to sub-ion range by means a detail comparison between in situ observations and hybrid numerical simulations. In particular we focus on properties magnetic field its component anisotropy Cluster measurements 2D First, address angular distribution wave-vectors kinetic ion electron scales studying variance components. When taking into account single-direction sampling performed spacecraft wind, main fluctuations observed are also recovered our description. This result confirms that turbulence is characterized quasi-2D gyrotropic k-vectors around mean field. then consider compressibility associated with evolution large-MHD scales. The ratio field-aligned perpendicular fluctuations, typically low inertial range, increases significantly when crossing value function total plasma beta only, as expected theoretical predictions, higher for beta. Moreover, observe this increase has gradual trend high values data; behaviour well captured level simulations fairly good agreement especially at beta, suggesting explored supported low-frequency highly-oblique pressure balance, like Alfven waves or other slowly evolving coherent structures.