PROPERTIES OF MAGNETOHYDRODYNAMIC TURBULENCE IN THE SOLAR-WIND AS OBSERVED BY ULYSSES AT HIGH HELIOGRAPHIC LATITUDES

The Ulysses mission provides an opportunity to study the evolution of magnetohydrodynamic (MHD) turbulence in pure highspeed solar wind stre ams. The absence at high heliocentric latitudes of the strong shears i n solar wind velocity generally present near the heliocentric current sheet allows investigation of how fluctuations in the magnetic field a nd plasma relax and evolve in the radially expanding solar wind. We re port results of an analysis of the radial and latitudinal variation of the turbulence properties of the fluctuations, especially various pla sma-field correlations, in high latitude regions. The results constrai n current theories of the evolution of MHD turbulence in the solar win d. Compared to similar observations at 0.3 AU by Hellos, we find spect ra that are similar in having a large frequency band with an f(1) powe r spectrum in the outward traveling component of the waves, followed a t higher frequencies by a steeper spectrum. Ulysses observations estab lish that at high latitudes the turbulence is less evolved (i.e., has a smaller inertial range) than it is in the ecliptic at the same helio centric distance, apparently due to the absence of strong velocity she ar. Once Ulysses is in the polar coronal hole, properties of the turbu lence appear to be determined by the heliocentric distance of the spac ecraft rather than by its helio-latitude.