Computer Simulations of Electrostatic Solitary Waves in the Magnetotail:
A Nonlinear Model of Broadband Electrostatic Noise


Y. Omura, H. Kojima, and H. Matsumoto
Radio Atmospheric Science Center, Kyoto University


We present computer simulations of the electrostatic solitary waves (ESW) as observed by GEOTAIL, which had been identified as broadband electrostatic noise (BEN) in the previous studies. We performed electrostatic particle simulations for various parameters and found conditions for generation of the ESW. The ESW is generated as a results of nonlinear coalescence of strong electrostatic waves excited by an electrostatic beam instability involving the electron beam drifting relative to the majority of ions and another electrons drifting with the ions. As a necessary condition for the ESW, the ion thermal velocity must be large enough so that the electrostatic waves due to the beam instability cannot decay to ion acoustic waves. The development of the ESW also depends on the density ratio of the two electron beams. The density of the electron beam drifting against the ions must be larger than about 30 % of the plasma density. We make a number of suggestions for future observations of particles and waves related to the BEN or ESW in the magnetotail.

Simulation Model:

Simulation Results:


For further details, please see

Y. Omura, H. Kojima and H. Matsumoto, Computer Simulation of Electrostatic Solitary Waves: A Nonlinear Model of Broadband Electrostatic Noise, Geophysical Research Letters, vol. 21, pages 2,923-2,926, 1994.





Acknowledgments


We thank H. Usui and T. Miyake for discussion concerning the computer simulations. We thank the GEOTAIL project team for providing exciting plasma wave data that shows a close similarity with the present simulation results. The computer simulations were done on the KDK computer system at Radio Atmospheric Science Center, Kyoto University.

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