Numerical simulations of solar wind turbulence

Alfvenic fluctuations are a ubiquitous component of the solar wind. Evidence from many spacecraft indicates that the fluctuations are convected out of the solar corona with relatively flat power spectra and constitute a source of free energy for a turbulent cascade of magnetic and kinetic energy to high wave numbers. Observations and simulations support the conclusion that the cascade evolves most rapidly in the vicinity of velocity shears and current sheets. Numerical solutions of the magnetohydrodynamic equations are clarifying not only how a turbulent cascade develops, but also the nature of the symmetries of the turbulence. Of particular interest is the origin of the Maltese cross two-dimensional correlation function of magnetic fluctuations that was deduced from ISEE 3 data. A central issue to be resolved is whether the correlation function indicates the existence of a quasi-two-dimensional component of the turbulence, or reflects another origin, such as pressure-balanced structures or small velocity shears. This paper reviews the current status of our simulations of turbulence in the solar wind. These simulations include a tilted rotating current sheet as well as variety of waves (e.g., Alfvenic, quasi-two-dimensional, pressure balance structures) and '' microstreams ''. Some aspects of our global models of heliospheric structure are also covered.