Trapping saturation of the bump-on-tail instability and electrostatic harmonic excitation in Earth's foreshock

Journal Article · Sat Sep 01 04:00:00 EDT 1990 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/JA095iA09p14905· OSTI ID:5312634

Klimas, A J ^[1]

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1. NASA Goddard Space Flight Center, Greenbelt, MD (USA)

Trapping saturation of the bump-on-tail instability is discussed using electron plasma Vlasov simulation results. The role of electrostatic harmonic excitation is considered in detail and shown to play a decisive role in the saturation of the instability. An extensive discussion of the simulation results is given to show that the results are not significantly limited by the finite number of Fourier modes used nor by the discrete distribution of those modes in wave number. It is argued that in the leading edge of Earth's electron foreshock a narrow wave number band of unstable field modes leads to trapping saturation of the bump-on-tail instability while simultaneously exciting electrostatic plasma waves at harmonics of the plasma frequency in simialr narrow bands of shorter wavelengths. The argument is based (1) on the observations of Lacombe et al. (1985), who found intense plasma waves at the leading edge of the foreshock with a spectral distribution sufficiently narrow to trap particles in resonance with the waves, and (2) on numerical simulations of the foreshock electron plasma which indicate that trapping saturation of the bump-on-tail instability leads to phase space vortex formation with consequent excitation of electrostatic harmonics. Thus it is suggested that observations of electrostatic harmonics in the leading edge of the foreshock would strongly implicate trapping as the saturation mechanism for the bump-on-tail instability in that region.

• OSTI ID: 5312634
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 95:A9; ISSN 0148-0227; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640201* -- Atmospheric Physics-- Auroral
Ionospheric
& Magetospheric Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
BUMP-IN-TAIL INSTABILITY
COMPUTERIZED SIMULATION
EARTH ATMOSPHERE
EARTH MAGNETOSPHERE
ELECTRONS
ELEMENTARY PARTICLES
FERMIONS
INSTABILITY
INTERACTIONS
INTERPLANETARY MAGNETIC FIELDS
LANGMUIR FREQUENCY
LEPTONS
MAGNETIC FIELDS
PLASMA INSTABILITY
PLASMA MICROINSTABILITIES
PLASMA WAVES
SHOCK WAVES
SIMULATION
SOLAR ACTIVITY
SOLAR WIND
TRAPPING
VORTICES