Ion Bernstein waves in a plasma with a kappa velocity distribution

Journal Article · Tue Oct 15 04:00:00 EDT 2013 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.4824615· OSTI ID:22218499

Nsengiyumva, F.; Mace, R. L.; Hellberg, M. A. ^[1]

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1. School of Chemistry and Physics, University of KwaZulu-Natal, Durban 4000 (South Africa)

Using a Vlasov-Poisson model, a numerical investigation of the dispersion relation for ion Bernstein waves in a kappa-distributed plasma has been carried out. The dispersion relation is found to depend significantly on the spectral index of the ions, κ{sub i}, the parameter whose smallness is a measure of the departure from thermal equilibrium of the distribution function. Over all cyclotron harmonics, the typical Bernstein wave curves are shifted to higher wavenumbers (k) if κ{sub i} is reduced. For waves whose frequency lies above the lower hybrid frequency, ω{sub LH}, an increasing excess of superthermal particles (decreasing κ{sub i}) reduces the frequency, ω{sub peak}, of the characteristic peak at which the group velocity vanishes, while the associated k{sub peak} is increased. As the ratio of ion plasma to cyclotron frequency (ω{sub pi}/ω{sub ci}) is increased, the fall-off of ω at large k is smaller for lower κ{sub i} and curves are shifted towards larger wavenumbers. In the lower hybrid frequency band and harmonic bands above it, the frequency in a low-κ{sub i} plasma spans only a part of the intraharmonic space, unlike the Maxwellian case, thus exhibiting considerably less coupling between adjacent bands for low κ{sub i}. It is suggested that the presence of the ensuing stopbands may be a useful diagnostic for the velocity distribution characteristics. The model is applied to the Earth's plasma sheet boundary layer in which waves propagating perpendicularly to the ambient magnetic field at frequencies between harmonics of the ion cyclotron frequency are frequently observed.

• OSTI ID: 22218499
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 10 Vol. 20; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
BERNSTEIN MODE
BOLTZMANN-VLASOV EQUATION
BOUNDARY LAYERS
CYCLOTRON HARMONICS
DISPERSION RELATIONS
DISTRIBUTION FUNCTIONS
ELECTROMAGNETIC RADIATION
IONS
LOWER HYBRID CURRENT DRIVE
LOWER HYBRID HEATING
MAGNETIC FIELDS
NUMERICAL ANALYSIS
PLASMA SHEET
PLASMA WAVES
POISSON EQUATION
THERMAL EQUILIBRIUM
VELOCITY