Three-dimensional electromagnetic strong turbulence. II. Wave packet collapse and structure of wave packets during strong turbulence

Journal Article · Fri Jul 15 04:00:00 EDT 2011 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.3603969· OSTI ID:22046875

Graham, D B; Robinson, P A; Cairns, Iver H ^[1]; Skjaeraasen, O ^[2]

---

1. School of Physics, University of Sydney, New South Wales 2006 (Australia)
2. ProsTek, Institute for Energy Technology, P.O. Box 40, N-2027 Kjeller (Norway)

Large-scale simulations of wave packet collapse are performed by numerically solving the three-dimensional (3D) electromagnetic Zakharov equations, focusing on individual wave packet collapses and on wave packets that form in continuously driven strong turbulence. The collapse threshold is shown to decrease as the electron thermal speed {nu}{sub e}/c increases and as the temperature ratio T{sub i}/T{sub e} of ions to electrons decreases. Energy lost during wave packet collapse and dissipation is shown to depend on {nu}{sub e}/c. The dynamics of density perturbations after collapse are studied in 3D electromagnetic strong turbulence for a range of T{sub i}/T{sub e}. The structures of the Langmuir, transverse, and total electric field components of wave packets during strong turbulence are investigated over a range of {nu}{sub e}/c. For {nu}{sub e}/c < or approx. 0.17, strong turbulence is approximately electrostatic and wave packets have very similar structure to purely electrostatic wave packets. For {nu}{sub e}/c > or approx. 0.17, transverse modes become trapped in density wells and contribute significantly to the structure of the total electric field. At all {nu}{sub e}/c, the Langmuir energy density contours of wave packets are predominantly oblate (pancake shaped). The transverse energy density contours of wave packets are predominantly prolate (sausage shaped), with the major axis being perpendicular to the major axes of the Langmuir component. This results in the wave packet becoming more nearly spherical as {nu}{sub e}/c increases, and in turn generates more spherical density wells during collapse. The results obtained are compared with previous 3D electrostatic results and 2D electromagnetic results.

• OSTI ID: 22046875
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 7 Vol. 18; 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
DISTURBANCES
ELECTRIC FIELDS
ELECTROMAGNETIC RADIATION
ELECTRON TEMPERATURE
ELECTRONS
ENERGY DENSITY
ION TEMPERATURE
IONS
NUMERICAL ANALYSIS
PLASMA
PLASMA DENSITY
PLASMA SIMULATION
PLASMA WAVES
THREE-DIMENSIONAL CALCULATIONS
TRANSVERSE ENERGY
TRAPPING
TURBULENCE
WAVE PACKETS