Zakharov simulations of Langmuir turbulence: Effects on the ion-acoustic waves in incoherent scattering

Journal Article · Fri Dec 15 00:00:00 EST 2006 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.2402145· OSTI ID:20860452

Guio, P; Forme, F ^[1]

---

1. Physics Department, University of Oslo, N-0316 Oslo (Norway)

This paper presents a numerical study of the effect of Langmuir turbulence on incoherent scatter spectra. The Langmuir turbulence is driven by low energy beams of electrons in the Earth's upper ionosphere above 300 km. The nonlinear coupling between Langmuir waves and ion-acoustic waves is governed by the Zakharov system of equations. The model is enhanced with stochastic forcing in order to estimate by how much over the thermal level the spectrum seen by an incoherent scatter radar will be enhanced. This also allows us to directly compare the modeled spectra to the observed spectra collected by the incoherent scattering technique, as well as to statistically investigate the signature of the modeled spectra through an exploratory data analysis. Results for different beam energies are presented, covering the regimes of weak as well as strong turbulence. The incoherent scatter spectra signature is discussed in light of these regimes. It is shown that incoherent scatter radar observations of enhanced ion-acoustic and/or Langmuir waves compared to thermal level can provide good estimates of the beam parameters and of the type of turbulent regime. The cascade regime leads to strongly asymmetric spectra with enhancements over a limited range of wave numbers. The cavitation regime leads to marginally asymmetric spectra, with enhancement over a wide range of wave numbers, and features a central peak for a limited range of wave numbers. Finally, it is shown that the Langmuir turbulence should be preferentially observed for scattering wavelengths large compared to the Debye length.

• OSTI ID: 20860452
• Journal Information: Physics of Plasmas, Vol. 13, Issue 12; Other Information: DOI: 10.1063/1.2402145; (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
ASYMMETRY
BEAM-PLASMA SYSTEMS
COMPARATIVE EVALUATIONS
COUPLING
DATA ANALYSIS
DEBYE LENGTH
ELECTRON BEAMS
ELECTRONS
INCOHERENT SCATTERING
ION ACOUSTIC WAVES
IONOSPHERE
IONS
NONLINEAR PROBLEMS
NUMERICAL ANALYSIS
PLASMA
PLASMA SIMULATION
STOCHASTIC PROCESSES
TURBULENCE
VISIBLE RADIATION