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Simulation studies of plasma waves in the electron foreshock - The generation of downshifted oscillationsThe generation of waves with frequencies downshifted from the plasma frequency, as observed in the electron foreshock, is analyzed by particle simulation. Wave excitation differs fundamentally from the familiar excitation of the plasma eigenmodes by a gentle bump-on-tail electron distribution. Beam modes are destabilized by resonant interaction with bulk electrons, provided the beam velocity spread is very small. These modes are stabilized, starting with the higher frequencies, as the beam is broadened and slowed down by the interaction with the wave spectrum. Initially a very cold beam is also capable of exciting frequencies considerably above the plasma frequency, but such oscillations are quickly stabilized. Low-frequency modes persist for a long time, until the bump in the electron distribution is completely 'ironed' out. This diffusion process also is quite different from the familiar case of well-separated beam and bulk electrons. A quantitative analysis of these processes is carried out.
Document ID
19900049931
Document Type
Reprint (Version printed in journal)
Authors
Dum, C. T. (MIT Cambridge, MA, United States)
Date Acquired
August 14, 2013
Publication Date
June 1, 1990
Publication Information
Publication: Journal of Geophysical Research
Volume: 95
ISSN: 0148-0227
Subject Category
PLASMA PHYSICS
Report/Patent Number
AFOSR-TR-90-1108
AD-A228766
Funding Number(s)
CONTRACT_GRANT: NAGW-1532
Distribution Limits
Public
Copyright
Other