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Goldstein et al. 1999
Goldstein, M.L., Roberts, D.A., Deane, A.E., Ghosh, S. and Wong, H.K. (1999). Numerical simulation of Alfvénic turbulence in the solar wind. Journal of Geophysical Research 104: doi: 10.1029/1998JA900128. issn: 0148-0227.

Low-frequency fluctuations in the solar wind magnetic field and plasma velocity are often highly correlated, so much so that the fluctuations can be thought of as nearly perfect Alfv¿n waves. Evidence from the Helios and Ulysses spacecraft suggest strongly that these fluctuations emanate from the solar corona with high correlation and flat power spectra (~f-1). These fluctuations constitute a source of free energy for a turbulent cascade of magnetic and kinetic energy to high wave numbers, a cascade that evolves most rapidly in the vicinity of velocity shears and the heliospheric current sheet. Numerical solutions of both the compressible and incompressible equations of magnetohydrodynamics (MHD) in Cartesian geometry showed that sharp gradients in velocity would decrease substantially the Alfv¿nicity of initially pure Alfv¿nic fluctuations; however, the effects of solar wind expansion on this turbulent evolution is, as yet, undetermined. We demonstrate that as was the case in Cartesian geometry, in an expanding volume, velocity shears and pressure-balanced flux tubes still reduce the Alfv¿nicity of parallel propagating wave packets. These three-dimensional spherically expanding simulations include velocity shears separating fast and slow flows, pressure-balanced flux tubes, and a central current sheet which is the site of magnetic reconnection. Two-dimensional spectra constructed in the r-&thgr; plane resemble closely those resulting from similar initial conditions in Cartesian geometry. ¿ 1999 American Geophysical Union

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Abstract

Keywords
Interplanetary Physics, MHD waves and turbulence, Space Plasma Physics, Numerical simulation studies, Space Plasma Physics, Turbulence, Interplanetary Physics, Solar wind plasma, Magnetospheric Physics, Polar cap phenomena, Space Plasma Physics, Waves and instabilities
Journal
Journal of Geophysical Research
http://www.agu.org/journals/jb/
Publisher
American Geophysical Union
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