Generation of filamentary structures by beam-plasma interaction

Journal Article · Mon May 15 00:00:00 EDT 2006 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.2197797· OSTI ID:20783033

Wang, X Y; Lin, Y ^[1]

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1. Physics Department, Auburn University, Auburn, Alabama 36849 (United States)

The previous simulations by Wang and Lin [Phys. Plasmas. 10, 3528 (2003)] showed that filaments, frequently observed in space plasmas, can form via the interaction between an ion beam and a background plasma. In this study, the physical mechanism for the generation of the filaments is investigated by a two-dimensional hybrid simulation, in which a field-aligned ion beam with relative beam density n{sub b}=0.1 and beam velocity V{sub b}=10V{sub A} is initiated in a uniform plasma. Right-hand nonresonant ion beam modes, consistent with the linear theory, are found to be dominant in the linear stage of the beam-plasma interaction. In the later nonlinear stage, the nonresonant modes decay and the resonant modes grow through a nonlinear wave coupling. The interaction among the resonant modes leads to the formation of filamentary structures, which are the field-aligned structures (k perpendicular B) of magnetic field B, density, and temperature in the final stage. The filaments are nonlinearly generated in a prey-predator fashion by the parallel and oblique resonant ion beam modes, which meanwhile evolve into two types of shear Alfven modes, with one mainly propagating along the background field B{sub 0} and the other obliquely propagating. The filamentary structures are found to be phase standing in the plasma frame, but their amplitude oscillates with time. In the dominant filament mode, fluctuations in the background ion density, background ion temperature, and beam density are in phase with the fluctuations in B, whereas the significantly enhanced beam temperature is antiphase with B. It is found that the filaments are produced by the interaction of at least two ion beam modes with comparable amplitudes, not by only one single mode, thus their generation mechanism is different from other mechanisms such as the stimulated excitation by the decay of an Alfven wave.

• OSTI ID: 20783033
• Journal Information: Physics of Plasmas, Vol. 13, Issue 5; Other Information: DOI: 10.1063/1.2197797; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ALFVEN WAVES
AMPLITUDES
BEAM-PLASMA SYSTEMS
DECAY
DENSITY
ELECTRON TEMPERATURE
EXCITATION
FILAMENTS
FLUCTUATIONS
ION BEAMS
ION DENSITY
ION TEMPERATURE
MAGNETIC FIELDS
NONLINEAR PROBLEMS
PLASMA
PLASMA DENSITY
PLASMA INSTABILITY
PLASMA SIMULATION
PLASMA WAVES
TWO-DIMENSIONAL CALCULATIONS