Numerical simulation of Alfvénic turbulence in the solar wind

We demonstrate that in an expanding volume, velocity shears and pressure-balanced flux tubes reduce the Alfvenicity of parallel propagating wave packets, as had been found previously in Cartesian geometry. The resulting power spectra have an inertial range spectral index of approximately 5/3. These three-dimensional spherically expanding simulations can include velocity shears separating fast and slow flows, pressure-balanced flux tubes, and a central current sheet. Two-dimensional spectra constructed in the r−θ plane resemble closely those resulting from similar initial conditions in Cartesian geometry.