Two-dimensional nonlinear dynamics of bidirectional beam-plasma instability

• Published in: Journal of Geophysical Research - Space Physics Vol. 114; no. A1; pp. A01106 - n/a
• Main Authors: Pavan, J., Ziebell, L. F., Gaelzer, R., Yoon, P. H.
• Format: Journal Article
• Language: English
• Published: Washington, DC American Geophysical Union 01-01-2009; Blackwell Publishing Ltd
• Subjects: beam-plasma instability; Earth sciences; Earth, ocean, space; Exact sciences and technology; Kinetic waves and instabilities; Mathematical and numerical techniques; Nonlinear phenomena; solar wind electrons; Space Plasma Physics; Turbulence; Wave/wave interactions; weak turbulence; weak turbulence; solar wind electrons; beam-plasma instability; Dimensionality; Mode coupling; Velocity space; anisotropy; Pitch angle; asymmetric distribution; Electron beam; asymmetry; aluminum; turbulence; electrons; lead; solar wind; drill cores; dynamics; Beam plasma instability; fluctuations; plateaus; populations; Wave number; direction; Non linear wave
• ISSN: 0148-0227; 2156-2202
• DOI: 10.1029/2008JA013557

Solar wind electrons near 1 AU feature wide‐ranging asymmetries in the superthermal tail distribution. Gaelzer et al. (2008) recently demonstrated that a wide variety of asymmetric distributions results if one considers a pair of counterstreaming electron beams interacting with the core solar wind electrons. However, the nonlinear dynamics was investigated under the simplifying assumption of one dimensionality. In the present paper, this problem is revisited by extending the analysis to two dimensions. The classic bump‐on‐tail instability involves a single electron beam interacting with the background population. The bidirectional or counterstreaming beams excite Langmuir turbulence initially propagating in opposite directions. It is found that the nonlinear mode coupling leads to the redistribution of wave moments along concentric arcs in wave number space, somewhat similar to the earlier findings by Ziebell et al. (2008) in the case of one beam‐plasma instability. However, the present result also shows distinctive features. The similarities and differences in the nonlinear wave dynamics are discussed. It is also found that the initial bidirectional beams undergo plateau formation and broadening in perpendicular velocity space. However, the anisotropy persists in the nonlinear stage, implying that an additional pitch angle scattering by transverse electromagnetic fluctuations is necessary in order to bring the system to a truly isotropic state.