Simulations of solar wind turbulence
M. L. Goldstein 1, A. V. Usmanov 1,2, D. A. Roberts 3
1 Code 673, NASA Goddard Space Flight Center, Greenbelt, MD 20771
2 Department of Physics and Astronomy and Bartol Research Institute, University of Delaware, Newark, DE 19716
3 Code 672, NASA Goddard Space Flight Center, Greenbelt, MD 20771
Recently we have restructured our approach to simulating magnetohydrodynamic (MHD) turbulence in the solar wind. Previously, we had defined a "virtual" heliosphere that contained, for example, a tilted rotating current sheet, microstreams, quasi-two-dimensional fluctuations, as well as Alfvén waves. In this new version of the code, we use the global, time-stationary, WKB Alfvén wave-driven solar wind model developed by Usmanov and described in Usmanov and Goldstein  to define the initial state of the system. Consequently, current sheets, and fast and slow streams are computed self-consistently from an inner, photospheric, boundary. To this steady-state configuration, we add fluctuations close to, but above, the surface where the flow becomes super-Alfvénic. The time-dependent MHD equations are then solved using a semi-discrete third-order Central Weighted Essentially Non-Oscillatory (CWENO) numerical scheme. The computational domain now includes the entire sphere; the geometrical singularity at the poles is removed using the multiple grid approach described in Usmanov . Wave packets are introduced at the inner boundary such as to satisfy Faraday's Law [Yeh and Dryer, 1985] and their nonlinear evolution are followed in time.