Whistler anisotropy instability at low electron {beta}: Particle-in-cell simulations
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
The whistler anisotropy instability is studied in a magnetized, homogeneous, collisionless plasma model. The electrons (denoted by subscript e) are represented initially with a single bi-Maxwellian velocity distribution with a temperature anisotropy T{sub perpendiculare}/T{sub ||e}>1, where perpendicular and || denote directions perpendicular and parallel to the background magnetic field B{sub o}, respectively. Kinetic linear dispersion theory predicts that, if the ratio of the electron plasma frequency {omega}{sub e} to the electron cyclotron frequency {Omega}{sub e} is greater than unity and {beta}{sub ||e}{>=}0.025, the maximum growth rate of this instability is at parallel propagation, where the fluctuating fields are strictly electromagnetic. At smaller values of {beta}{sub ||e}, however, the maximum growth rate shifts to propagation oblique to B{sub o} and the fluctuating electric fields become predominantly electrostatic. Linear theory and two-dimensional particle-in-cell simulations are used to examine the consequences of this transition. Three simulations are carried out, with initial {beta}{sub ||e}=0.10, 0.03, and 0.01. The fluctuating fields of the {beta}{sub ||e}=0.10 run are predominantly electromagnetic, with nonlinear consequences similar to those of simulations already described in the literature. In contrast, the growth of fluctuations at oblique propagation in the low electron {beta} runs leads to a significant {delta}E{sub ||}, which heats the electrons leading to the formation of a substantial suprathermal component in the electron parallel velocity distribution.
- OSTI ID:
- 22043418
- Journal Information:
- Physics of Plasmas, Vol. 18, Issue 8; Other Information: (c) 2011 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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