HR: 16:00h
AN: SH44A-01 INVITED     [Abstracts]
TI: The low frequency spectrum of solar wind turbulence and its relationship to wave dissipation in the solar corona
AU: * Goldstein, M L
EM: melvyn.l.goldstein@nasa.gov
AF: NASA Goddard Space Flight Center, Code 692, Greenbelt, MD 20771 United States
AB: Present theories and models of coronal heating and solar wind acceleration have difficulty matching observed solar wind parameters while simultaneously satisfying important observational constraints. These constraints include the strong indication from Helios data that the source spectrum of solar wind magnetic fluctuations has a $1/f$ power spectrum. If one assumes that the spectrum at the base of the corona is $1/f$ (which might arise from a kinematical superposition of signals due to scale-invariant reconnection of magnetic structures on the solar surface), then one must construct a theory that progresses from topological rearrangement of magnetic fields to a frequency spectrum at the top of the corona that has a $1/f$ spectrum. Progress has also been made in understanding how other photospheric motions might generate the observed spectral power. One difficulty with such theories is that even when one initiates such calculations with a $1/f$ spectrum, the spectra at the out-flow boundary have evolved to be steeper than $1/f$. Damping that occurs only near the cyclotron frequency might preserve an initial $1/f$ spectrum, but that has yet to be demonstrated. One alternative (explored by {\it Dmitruk et al.} [2002] and {\it Oughton et al.} [2001]) is that the initial fluctuations give rise to a reduced magnetohydrodynamic (RMHD), quasi-two-dimensional cascade of $k_\bot$ modes that heat the corona. The fluctuating power in $k_\parallel$ then escapes into the solar wind. Simulations to date, however, cannot maintain a $1/f$ spectrum because the dissipation in the simulations is broadband. Another observation that theories of wave heating and acceleration of the corona must address is that the total energy available from waves to heat the corona and accelerate the fast solar wind appears to be inadequate. \hangindent=10pt Dmitruk, P., W.H. Matthaeus, L.J. Milano, S. Oughton, G.P. Zank, and D.J. Mullan, Coronal heating distribution due to low-frequency, wave-driven turbulence, {\it The Astrophys. J., 575} (1), 571-577, 2002. \hangindent=10pt Oughton, S., W.H. Matthaeus, P. Dmitruk, L.J. Milano, G.P. Zank, and D.J. Mullan, A reduced magnetohydrodynamic model of coronal heating in open magnetic regions driven by reflected low-frequency Alfv\'en waves, {\it The Astrophys. J., 551} (1), 565-575, 2001.
DE: 2162 Solar cycle variations (7536)
DE: 2164 Solar wind plasma
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2004 AGU Fall Meeting