HR: 0800h
AN: SH51B-1207    [Abstracts]
TI: Polarization Properties of High Frequency Waves in Solar Wind and Electron Foreshock Regions: WIND Observations and Interpretation
AU: * Dudok de Wit, T
EM: ddwit@cnrs-orleans.fr
AF: LPCE, UMR 6115 CNRS and Univ. of Orleans 3A avenue de la Recherche Scientifique, Orleans, 45071 France
AU: Krasnosselskikh, V
EM: vkrasnos@cnrs-orleans.fr
AF: LPCE, UMR 6115 CNRS and Univ. of Orleans 3A avenue de la Recherche Scientifique, Orleans, 45071 France
AU: Bale, S D
EM: bale@ssl.berkeley.edu
AF: Space Sciences Laboratory, University of California, Berkeley, CA 94720-7450 United States
AB: The electron foreshock and the upstream solar wind exhibit a variety of nonlinear phenomena, among which wave-wave interactions around the plasma frequency have received much interest [1,2]. A conspicuous feature is the occurrence of coherent quasi-monochromatic wave packets with close frequencies. Although such spectra are now known to be the signature of the nonlinear decay of Langmuir waves, many open questions remain. Here we consider their polarisation properties to put further constraints on their interpretation. Our analysis is based on high-frequency electric field measurements made by the WIND satellite in the terrestrial electron foreshock. Two components of the electric field, sampled at 120 kHz, are available. Using a demodulation technique, we show how to extract the polaristion properties of the waves and compare these to the orientation of the magnetic field. The main observed feature is a quasi co-planarity of the k-vectors of the primary and secondary waves, and their closeness to the direction of the background magnetic field. These results give a strong argument in favour of the theoretical model of beam-plasma interaction, where the saturation of the wave amplitude is determined by the decay instability. This is further supported by the orientation of the k-vector of the secondary wave, which is preferentially opposite to that of the primary wave. [1] S. Bale et al., On the amplitude of intense Langmuir waves in the terrestrial electron foreshock, JGR 102 (1997) 11281 [2] J. Soucek et al., Nonlinear decay of foreshock Langmuir waves in the presence of plasma inhomogeneities: theory and CLUSTER observations, JGR 110, A080102 (2005)
DE: 2411 Electric fields (2712)
DE: 2724 Magnetopause and boundary layers
DE: 2752 MHD waves and instabilities (2149, 6050, 7836)
DE: 2772 Plasma waves and instabilities (2471)
SC: SPA-Solar and Heliospheric Physics [SH]
MN: Fall Meeting 2005