HR: 0800h
AN: SM41B-1184    [Abstracts]
TI: Nonlinear evolution of the electron two-stream instability: Two-dimensional particle simulations
AU: * Umeda, T
EM: taka@igpp.ucla.edu
AF: Institute of Geophysical and Planetary Physics, University of California, Los Angeles, Slichter Hall, 405 Hilgard Ave., Los Angeles, CA 90095-1567 United States
AU: Omura, Y
EM: omura@rish.kyoto-u.ac.jp
AF: Research Institute for Sustainable Humanosphere, Kyoto University, Gokasho, Uji, Kyoto, 611-0011 Japan
AU: Miyake, T
EM: miyake@rdw.pu-toyama.ac.jp
AF: Toyama Prefectural University, Kosugi, Toyama, 930-0398 Japan
AU: Matsumoto, H
EM: matsumot@rish.kyoto-u.ac.jp
AF: Research Institute for Sustainable Humanosphere, Kyoto University, Gokasho, Uji, Kyoto, 611-0011 Japan
AU: Ashour-Abdalla, M
EM: mabdalla@igpp.ucla.edu
AF: Institute of Geophysical and Planetary Physics, University of California, Los Angeles, Slichter Hall, 405 Hilgard Ave., Los Angeles, CA 90095-1567 United States
AU: Ashour-Abdalla, M
EM: mabdalla@igpp.ucla.edu
AF: Department of Physics and Astronomy, University of California, Los Angeles, Knudsen Hall, Los Angeles, CA 90095-1547 United States
AB: We have studied the nonlinear evolution of electron two-stream instabilities in a two-dimensional system. Electron two-stream and bump-on-tail instabilities are considered to be the most probable generation mechanisms for electrostatic solitary waves and electron holes observed in various regions of the Earth's magnetosphere. We performed two-dimensional electromagnetic particle simulations for various sets of the electron cyclotron frequencies and initial electron thermal velocities, and found that the nonlinear evolution falls into four groups. Under a very weak ambient magnetic field such that the electron cyclotron frequency is smaller than the bounce frequency of electrons trapped by electron holes, the electron holes are unstable as reported in previous simulation studies. When the electron cyclotron frequency is larger than the bounce frequency but is smaller than twice the bounce frequency, we found formation of two-dimensional electron holes isolated in both directions parallel and perpendicular to the ambient magnetic field. The two-dimensional electron holes persist for several hundred of electron plasma oscillation periods. When the electron cyclotron frequency is much larger than the electron bounce frequency, the stability of electron holes is controlled by their amplitudes. In runs with high initial electron thermal velocities, the two-stream instability develops to form stable one-dimensional electron holes through coalescence. On the other hand, in the case of the cold two-stream instability, the potential energy of electron holes becomes larger than the thermal energy of electrons, and electron holes decay into electrostatic whistler waves.
DE: 6944 Nonlinear phenomena (4400, 7839)
DE: 6984 Waves in plasma (7867)
DE: 7815 Electrostatic structures
DE: 7829 Kinetic waves and instabilities
DE: 7852 Solitons and solitary waves (4455)
SC: SPA-Magnetospheric Physics [SM]
MN: Fall Meeting 2005