Speaker
Description
Plasma turbulence is an inherently multi-scale phenomenon that spans a vast range of spatial and temporal scales. In the solar wind, the inertial-range turbulent cascade extends over nearly four decades in length (from injection scales down to ion characteristic scales), and six decades when including electron characteristic scales. Being able to self-consistently simulate such a dynamics is nowadays computationally impossible, even in two dimensions. Here we present the multi-scale Box-in-Box (BiB) method, an innovative framework we developed to model the plasma dynamics over a massive range of scales. The method hierarchically couples several simulations: the turbulent energy cascade is firstly simulated at very large scales by means of a classic MHD description, then a selected subdoimain (box) of the large simulation is used as initial condition for a second simulation with higher resolution. This procedure can be repeated multiple times in sequence, possibly embedding increasingly complex plasma models (MHD, hybrid, and fully kinetic). As a proof-of-concept, we show results of a BIB simulation that reproduce the spectral properties of solar wind turbulence over more than four decades, from the outer correlation scale down to sub-ion scales, by coupling one MHD simulation and two Hall-MHD simulations. The BiB approach preserves key turbulent features, such as the cross-scale energy transfer, while reducing the computational costs by roughly ten thousand times. This methodology opens new pathways for addressing fundamental questions in space and astrophysical plasmas, enabling self-consistent exploration of turbulence across a range of scales that were previously concurrently inaccessible.
