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 [2003] 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 [1996]. 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.