Speaker
Description
The energy cascade in Alfvénic solar wind turbulence is often analyzed under the ideal plasma approximation, where viscosity (ν) and resistivity (η) are assumed equal and negligible. Recent observations, however, indicate that viscous effects associated with velocity fields may operate on scales significantly larger than those of magnetic dissipation. To address this, we introduce a phenomenological framework that distinguishes between viscous and resistive dissipation by allowing ν and η to take different values.
Within this approach, we examine the third-order Yaglom law for magnetohydrodynamic (MHD) turbulence by combining theoretical derivations with high-resolution numerical simulations. The MHD energy budget is reformulated in terms of Elsässer variables, resulting in a modified von Kármán–Howarth equation appropriate for the visco-resistive case. The generalized Yaglom relation obtained in this context provides a direct estimate of the energy transfer rate across scales and highlights the deviations from the ideal MHD prediction.
The results from direct numerical simulations confirm the validity of the analytical model and demonstrate the impact of distinct viscous and resistive dissipation mechanisms on the turbulent cascade. These findings offer a refined framework for interpreting in-situ measurements of solar wind and magnetosheath turbulence.
