Simulations of Solar Wind Turbulence

Abstract

Simulations of magnetofluid turbulence using a variety of techniques for solving the equations of magnetohydrodynamics have elucidated many aspects of the evolution and properties of the solar wind. In particular, the simulations have shown the important role of velocity shear in driving the evolution of turbulence. MHD simulations have demonstrated the initiation of turbulent cascades arising from an initial packet of Alfven´ waves, the evolution of cross helicity (the correlation between the fluctuating magnetic and velocity field components), and the formation and evolution of corotating interaction regions. Puzzles remain, however. For example, simulations to date have not provided a satisfactory explanation of the observation that the direction of minimum variance of magnetic fluctuations tends to be oriented along the direction of the background magnetic field. We report preliminary studies indicating that transverse structures, including velocity shear, are essential to explain satisfactorily the evolution of the minimum variance of solar wind magnetic fluctuations.