Ion Bernstein instability in the terrestrial magnetosphere: Linear dispersion theory

• Published in: Journal of Geophysical Research: Space Physics Vol. 115; no. A12
• Main Authors: Gary, S. Peter, Liu, Kaijun, Winske, Dan, Denton, Richard E.
• Format: Journal Article
• Language: English
• Published: Washington, DC Blackwell Publishing Ltd 01.12.2010; American Geophysical Union
• Subjects: Atmospheric sciences; Earth sciences; Earth, ocean, space; Exact sciences and technology; Magnetic fields; Magnetism; magnetosonic waves; plasma instability; Plasma physics; Space; Velocity; Velocity distribution; Wavelengths; wavelength; waves; magnetic field; growth rates; density; Proton temperature; Collisionless plasma; Cyclotron frequency; Bernstein mode; amber; Instability growth rates; Velocity distribution; electrons; magnetosphere; fluctuations; instability; protons; ions; kinetics; dispersion; theory; direction
• ISSN: 0148-0227; 2169-9380; 2156-2202; 2169-9402
• DOI: 10.1029/2010JA015965

Linear kinetic dispersion theory for electromagnetic fluctuations in a homogeneous, magnetized, collisionless plasma is used to study the properties of an ion Bernstein mode instability driven by a proton velocity distribution fp(v) such that ∂fp(ν⊥)/∂ν⊥ > 0, where ⊥ denotes directions perpendicular to the background magnetic field Bo. Here fp(v) = f1(ν) − f2(ν), where f1 and f2 are Maxwellian velocity distributions with slightly different densities and temperatures; plasma parameters are taken from magnetospheric observations. Then the growth rate of this instability has relative maxima at ωr ≃ nΩp, where n = 1, 2, 3, … and Ωp is the proton cyclotron frequency; wave vector k at 0 < k∥ ≪ k⊥, where ∥ and ⊥ denote the directions parallel and perpendicular to Bo; and wavelengths of the order of or smaller than the proton gyroradius. The maximum instability growth rate is a monotonically decreasing function of the electron‐to‐proton temperature ratio but has its largest value at an intermediate value of the proton β (∼0.5 for the parameters considered here).