HR: 1330h
AN: SH43A-15    [Abstracts]
TI: Characteristics of Langmuir electric field waveforms and power spectra in the Earth's electron and ion foreshocks
AU: * Sigsbee, K
EM: kristine-sigsbee@uiowa.edu
AF: University of Iowa, Department of Physics and Astronomy, 203 Van Allen Hall, Iowa City, IA 52242 United States
AU: Kletzing, C A
EM: craig-kletzing@uiowa.edu
AF: University of Iowa, Department of Physics and Astronomy, 203 Van Allen Hall, Iowa City, IA 52242 United States
AU: Pickett, J S
EM: pickett@uiowa.edu
AF: University of Iowa, Department of Physics and Astronomy, 203 Van Allen Hall, Iowa City, IA 52242 United States
AU: Gurnett, D A
EM: donald-gurnett@uiowa.edu
AF: University of Iowa, Department of Physics and Astronomy, 203 Van Allen Hall, Iowa City, IA 52242 United States
AU: Balogh, A
EM: a.balogh@ic.ac.uk
AF: Imperial College, Space and Atmospheric Physics Group, The Blackett Laboratory, Prince Consort Road, London, SW7 2BW United Kingdom
AU: Lucek, E
EM: e.lucek@ic.ac.uk
AF: Imperial College, Space and Atmospheric Physics Group, The Blackett Laboratory, Prince Consort Road, London, SW7 2BW United Kingdom
AB: The characteristics of Langmuir waves observed by the Cluster WBD Plasma Wave Receiver in different regions of the Earth's foreshock are presented. Our previous work on waves in the electron foreshock has shown that the electric field amplitude probability distributions for Langmuir waves observed by Cluster can follow a combination of the log-normal statistics predicted by stochastic growth theory and power law statistics. Power law deviations from log-normal statistics are often the result of spatial averaging, but can also be found for large amplitude waves near the edge of the electron foreshock, which may show evidence of non-linearity. This raises questions about the possible effects of non-linear processes on the amplitude statistics. We examine the significance of non-linear processes in the foreshock by considering the various types of Langmuir wave power spectra observed in this region. Evidence for non-linear processes such as parametric decay, has been found in Earth's electron foreshock in the form of wave spectra with double peaks near the plasma frequency. Away from the boundary between the foreshock and solar wind, Langmuir waves have been observed to shift up and down in frequency from the local plasma frequency. Far downstream, in the ion foreshock, the behavior of waves near the plasma frequency appears to be influenced by the presence of ULF waves. For selected cases, we discuss the occurrence rates of these types of Langmuir wave spectra in different regions of the Earth's foreshock.
DE: 2154 Planetary bow shocks
DE: 2159 Plasma waves and turbulence
DE: 2784 Solar wind/magnetosphere interactions
DE: 7839 Nonlinear phenomena
DE: 7868 Wave/wave interactions
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2005 Joint Assembly