HR: 0800h
AN: SH51C-0287    [Abstracts]
TI: Rapid Density Fluctuations in the Solar Wind
AU: * Kellogg, P J
EM: kellogg@waves.space.umn.edu
AF: University of Minnesota, 116 Church St. SE, Minneapolis, MN 55455 United States
AU: Horbury, T S
EM: t.horbury@imperial.ac.uk
AF: Imperial College, Blackett Lab, Prince Consort Road, London, SW72BW United Kingdom
AB: Using the EFW experiment on the Cluster spacecraft, rapid electron density fluctuations ( up to 2.5 Hz) in the solar wind have been studied, with the aim of understanding their nature and cause. The density fluctuation spectra obtained from the EFW probe potential variations are in rough agreement with earlier, OGO 5, measurements of ion density fluctuations. The electric fields corresponding to the electron density fluctuations are extremely small compared with what would be obtained if the electron fluctuations were not cancelled out by nearly equal ion density fluctuations, so that the fluctuations have the nature of ion acoustic waves. The electric field spectrum is more concentrated toward larger wave number,than the density spectrum, as would also be expected for ion acoustic waves. Correlation with magnetic fluctuations is weak, as is expected as magnetic fluctuations are known to be nearly incompressible. Nevertheless there are indications of pressure balance structures. Pressure balance structures are the nearly perpendicular propagation limit of ion acoustic waves. As ion acoustic waves are strongly damped in plasmas like the solar wind, it has always been a puzzle as to why they are found there. We speculate that these high frequency waves are created by mode conversion from magnetic fluctuations, and may represent part of the dissipation process for these.
DE: 7800 SPACE PLASMA PHYSICS
DE: 7815 Electrostatic structures
DE: 7863 Turbulence
DE: 7871 Waves and instabilities
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2004 AGU Fall Meeting