Magnetic fluctuation spectrum in the interplanetary medium

Waves and turbulence are ubiquitous in the solar wind. Whereas Alfven waves and Kolmogorov-type energy spectra are found at low frequencies, whistler waves and significant steeper magnetic fluctuation power law spectra are detected at frequencies higher than a fraction of hertz at one astronomical units. This. multi-scale turbulence behavior may be investigated in the framework of 3D Hall magnetohydrodynamics. In this case, both wave turbulence analysis and high Reynolds number simulations of strong turbulent flows converge towards a steepening of magnetic spectra which may be attributed to dispersive nonlinear processes rather than pure dissipation as often stated for the solar wind. A heuristic model of anisotropic Hall MHD turbulence is proposed to describe both weak wave and strong turbulence as well as the transition between these regimes.