Nonresonant low-frequency instabilities in multibeam plasmas: Applications to cometary environments and plasma sheet boundary layers

Journal Article · Wed May 01 00:00:00 EDT 1991 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/91JA00254· OSTI ID:5259524

Verheest, F ^[1]; Lakhina, G S ^[2]

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1. Physical Research Lab., Ahmedabad (India)
2. Indian Institute of Geomagnetism, Bombay (India)

Low-frequency electromagnetic fluctuations dominate the wave spectrum observed during strong plasma flows in the region upstream of a cometary nucleus and in the plasma sheet boundary layer of the Earth's magnetotail. A theoretical framework is established in the long-wavelength limit for nonresonant instabilities in a multibeam plasma, for any number of beams. Both the growth rates of the instabilities and the ultimate levels of magnetic field turbulence are given. A two-beam plasma models the contamination of the upstream solar wind by cometary material, whereas a three-beam model is invoked for the plasma sheet boundary layer, with two counterstreaming proton beams in the presence of an oxygen beam. If the two proton beams by themselves already excite a low-frequency instability, the injection of oxygen at rest in the center-of-mass frame does not chaneg the instability characteristics. Where the two proton beams alone are stable, a sufficient amount of oxygen with a sufficient velocity offset in the center-of-mass frame can render the plasma sheet boundary layer unstable. In both cases, the theoretical levels of low-frequency turbulence are in good agreement with observations and/or numerical simulations.

• OSTI ID: 5259524
• Journal Information: Journal of Geophysical Research; (United States), Vol. 96:A5; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
COMETS
PLASMA INSTABILITY
MAGNETOTAIL
ALFVEN WAVES
INSTABILITY GROWTH RATES
IONS
MAGNETIC FIELDS
OXYGEN
PLASMA DRIFT
PLASMA SIMULATION
SOLAR WIND
TURBULENCE
CHARGED PARTICLES
EARTH ATMOSPHERE
EARTH MAGNETOSPHERE
ELEMENTS
HYDROMAGNETIC WAVES
INSTABILITY
NONMETALS
SIMULATION
SOLAR ACTIVITY
640107* - Astrophysics & Cosmology- Planetary Phenomena
640201 - Atmospheric Physics- Auroral
Ionospheric
& Magetospheric Phenomena