Engineering topics

Payne, G. L.

Publications and source records attributed to Payne, G. L..

8 records

NASA NTRS1992

A hybrid Zakharov particle simulation of ionospheric heating

A 1D hybrid simulation model incorporating one of the Zakharov equations for the high-frequency waves and a particle-in-cell simulation of the ions is described and applied to ionospheric heating using realistic parameters. Results from the hybrid simulation are compared with a Zakharov simulation that incorporates a phenomenological model of ion damping. Both the hybrid and Zakharov simulations predict the formation of solitonlike waves. The early time behavior of the two simulations is different due to the high noise level in the hybrid simulation, but the late time behavior is quite similar.

Clark, K. L.↗

NASA NTRS1990

Particle simulation of Langmuir turbulence during ionospheric heating

Ionospheric heating leads to strong Langmuir turbulence including modulational instability, soliton formation, and spatial collapse. The Zakharov model usually used to describe these effects contains a low-frequency ion-acoustic wave equation which cannot be rigorously justified in the ionosphere where the electron and ion temperatures are comparable. In the present work, the low-frequency physics is described by a many-ion computer simulation. While some differences are found, the results for the most part confirm the earlier, much less difficult, Zakharov calculations.

Clark, K. L.↗

NASA NTRS1989

Numerical test of weak turbulence theory

The analytic theory of weak Langmuir turbulence is well known, but very little has previously been done to compare its predictions with numerical solutions of the basic dynamical evolution equations. In this paper, numerical solutions of the statistical weak turbulence theory are compared with numerical solutions of the Zakharov model of Langmuir turbulence, and good agreement in certain regimes of very weak field strength is found.

Payne, G. L.↗

NASA NTRS1984

Modulational instability and soliton formation during ionospheric heating

The most intense electric fields during ionospheric heating occur a fraction of a kilometer below the classical reflection point. At this location, the nonlinear evolution of Langmuir waves is studied within the context of the modified Zakharov equations. It is found that the modulational instability (oscillating two-stream instability) is more important than the three-wave parametric decay instability, leading to the rapid formation of solitons.

Payne, G. L.↗

NASA NTRS1984

Solitons versus parametric instabilities during ionospheric heating

Various effects associated with ionospheric heating are investigated by numerically solving the modified Zakharov (1972) equations. It is shown that, for typical ionospheric parameters, the modulational instability is more important than the parametric decay instability in the spatial region of strongest heater electric field. It is concluded that the modulational instability leads to the formation of solitons, as originally predicted by Petviashvili (1976).

Nicholson, D. R.↗

NASA NTRS1982

Solitons and ionospheric modification

The possibility of Langmuir soliton formation and collapse during ionospheric modification is investigated. Parameters characterizing former facilities, existing facilities, and planned facilities are considered, using a combination of analytical and numerical techniques. At a spatial location corresponding to the exact classical reflection point of the modifier wave, the Langmuir wave evolution is found to be dominated by modulational instability followed by soliton formation and three-dimensional collapse. The earth's magnetic field is found to affect the shape of the collapsing soliton. These results provide an alternative explanation for some recent observations.

Sheerin, J. P.↗

NASA NTRS1982

Solitons and ionospheric heating

It is noted that for parameters characterizing the Platteville ionospheric heating facility, the Langmuir wave evolution at the exact reflection point of the heater wave involves an oscillating two-stream instability followed by a collisionally damped three-dimensional soliton collapse. The result gives an alternative explanation for certain experimental observations.

Weatherall, J. C.↗

NASA NTRS1981

Weak double layers

The characteristics of weak double layers with potential steps approximately equal to five are investigated in a triple plasma device and compared with a kinetic model. The double layers considered here differ from those previously investigated in two significant ways: (1) the double layers are much weaker; and (2) trapped ions play a much less important role. In this study, two plasmas at different potentials but with similar characteristics are separated from a target chamber by grids so that ions enter only at the high potential side and electron beams enter at the low potential side. What is more, thermal electrons enter at the high potential side and are trapped by the double layer. The model calculations illustrate the role of the trapped ions in determining the position of the double layer, and they demonstrate the dependence of the length of the double layer on the entering ion and electron fluxes.

Hershkowitz, N.↗