Large-scale simulations of 2-D fully kinetic Farley-Buneman turbulence

Abstract

Abstract. Currents flowing in the Earth's ionospheric electrojets often develop Farley-Buneman (FB) streaming instabilities and become turbulent. The resulting electron density irregularities cause these regions to readily scatter VHF and UHF radar signals. Many of the observed characteristics of these radar measurements result from the nonlinear behavior of this plasma. This paper describes a set of high-resolution, 2-D, fully kinetic simulations of electric field driven turbulence in the electrojet. These show the saturated amplitude of the waves; coupling between linearly growing modes and damped modes; the evolution of the system from dominance by shorter (1 m-5 m) to longer (10 m-200 m) wavelength modes; and the propagation of the dominant modes at phase velocities that lie below the linearly predicted phase velocity and close to but slightly above the acoustic velocity. These simulations reproduce many of the observational characteristics of type 1 waves. They provide information useful in accurately modeling FB turbulence and demonstrate the significant progress we have made in simulating the electrojet.

The equatorial E-region and its plasma instabilities: a tutorial

“…Meers Oppenheim and his colleagues have pioneered in the recent work (see, e.g., Oppenheim et al, 2008a, and earlier references therein). These results, especially the movies that you can't put in a paper figure, show how the waves can limit in a purely 2-D simulation in a plane perpendicular to B.…”

“…In fact, we do not yet know if the dominant nonlinear limiting mechanism is two-dimensional (aspect angle effects are unimportant) or three-dimensional (coupling to damped waves propagating at off-perpendicular angles is the primary loss mechanism). There is a considerable literature covering analytical and numerical studies of 2-D mode coupling; see for example St.-Maurice and Hamza (2001), Otani and Oppenheim (2006), Oppenheim et al (2008a), and earlier references therein. Unfortunately numerical simulations are still Fig.…”

Modeling of the Farley-Buneman instability in the E-region ionosphere: a new hybrid approach

“…The effect of wave-front tilting has been observed in previous simulations with PIC ions (e.g. Janhunen, 1994;Oppenheim and Dimant, 2004;Oppenheim et al, 2008). Dimant and Oppenheim (2004) attributed this effect to the additional instability driving mechanism of the ion-thermal nature.…”

“…Even properly rescaled, such computational results not fully model the actual physical situation. Furthermore, numerical studies of wave activity have been mostly limited to 2-D cases: either in the plane parallel to the magnetic field (Machida and Goertz, 1988;Schlegel and Thiemann, 1994) or in the perpendicular plane (Newman and Ott, 1981;Janhunen, 1994;Oppenheim and Dimant, 2004;Dyrud et al, 2006;Oppenheim et al, 2008). The latter simulations are more relevant to the actual situation because they correctly take into account the dominant electron nonlinearity associated with the fluid-model term ∝δE×∇δn e , where δE and δn e are the turbulent electric field and electron density perturbations, respectively.…”

“…Nonlinear simulations of the FB instability are based on the two-fluid (Newman and Ott, 1981), particlein-cell (PIC) (Machida and Goertz, 1988;Schlegel and Thiemann, 1994;Janhunen, 1994;Oppenheim and Dimant, 2004;Oppenheim et al, 2008), or hybrid Dyrud et al, 2006) -semifluid, semi-PIC -codes. Note that for the FB instability, the kinetic effect of ion Landau damping is crucial because it gives the short-wavelength restriction on linearly unstable spectral domain.…”