Simulation studies of plasma waves in the electron foreshock: The transition from reactive to kinetic instability

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

DOI:https://doi.org/10.1029/JA095iA06p08111· OSTI ID:5223497

Dum, C T ^[1]

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1. Max-Planck-Institut fur Physik und Astrophysik, Garching (West Germany) Massachusetts Inst. of Tech., Cambridge (USA)

The electron beam-plasma instability is analyzed in particle simulation experiments, starting with a beam of small velocity spread. The dispersion relation is solved for snapshots of the actual evolving electron distribution function, rather than for the usual models consisting of Maxwellians. As the beam broadens, the analysis shows a transition from reactive beam modes, with frequencies extending much below the plasma frequency {omega}{sub e}, to kinetic instability of Langmuir waves, {omega}{approx}{omega}{sub e}, which is in agreement with the frequencies and growth rates observed in the simulation. Beam evolution is also in agreement with quasi-linear theory, except at the end of the reactive phase when trapping of beam electrons is seen. Although the spectrum temporarily narrows at this stage, there are, in contrast to previous simulations, still many modes present. the system then can proceed to a kinetic phase in which quasi-linear theory is again applicable. This stage is identical with the evolution starting from a gentle broad beam, except that wave levels are several times higher. With higher wave levels, mode coupling effects are also more prominent, but are still unable to prevent plateau formation. In contrast to the Langmuir wave regime, the reactive broadband wave regime lasts only for a relatively short period. In the electron foreshock it could only persist if a narrow beam or a sharp cutoff feature were maintained by continued beam injection and the time-of-flight mechanism.

• OSTI ID: 5223497
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 95:A6; ISSN JGREA; ISSN 0148-0227
• Country of Publication: United States
• Language: English

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71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
BEAM-PLASMA SYSTEMS
BEAMS
COMPUTERIZED SIMULATION
DISPERSION RELATIONS
DISTRIBUTION FUNCTIONS
EARTH ATMOSPHERE
EARTH MAGNETOSPHERE
ELECTRON BEAMS
ELECTRONS
ELEMENTARY PARTICLES
FERMIONS
FUNCTIONS
INSTABILITY
INTERACTIONS
INTERPLANETARY SPACE
LEPTON BEAMS
LEPTONS
PARTICLE BEAMS
PLASMA WAVES
QUASILINEAR PROBLEMS
REFLECTION
SHOCK WAVES
SIMULATION
SOLAR ACTIVITY
SOLAR WIND
SPACE