HR: 09:25h
AN: SH31B-06    [Abstracts]
TI: The Evolution of the Spectrum of Velocity Fluctuations in the Solar Wind
AU: * Roberts, D A
EM: aaron.roberts@nasa.gov
AF: NASA GSFC, Code 672, Greenbelt, MD 20771, United States
AB: Previous studies have shown that the power spectra of the magnetic field and velocity in the solar wind do not evolve in the same way with helocentric distance. In particular, the velocity spectrum remains flatter for a substantial distance. However, Voyager observations of the velocity spectrum have demonstrated a likely asymptotic state in which the spectrum steepens to having a spectral index of -5/3, finally mathching the magnetic spectrum and the theoretical expectation of Kolmogoroff turbulence. Here we examine evidence from other spacecraft, in particular studying Ulysses spectra to determine if the Voyager result, based on a very few sufficiently complete intervals, is correct. Preliminary results confirm the -5/3 slope for velocity fluctuations at ~5 AU from the Sun in the ecliptic. We will examine many intervals to develop a more general picture of the spectral evolution in various conditions, and how magnetic and velocity spectra differ in these cases.
DE: 2149 MHD waves and turbulence (2752, 6050, 7836)
DE: 2159 Plasma waves and turbulence
DE: 2164 Solar wind plasma
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2007 Fall Meeting