Nonlinear simulations of Type I irregularities in the equatorial electrojet

Thesis/Dissertation · Mon Jan 01 04:00:00 EST 1979

OSTI ID:6168167

Newman, A L

Nonlinear two-dimensional numerical models have been developed in order to examine the time evolution of the growth and saturation of the two-stream instability under conditions corresponding to those in the equatorial electrojet. The non-linear quasineutral fluid equations of motion for electrons and ions, as well as the respective continuity equations, are integrated in time by employing Richtmeyer's second-order form of the Lax-Wendroff method. Artificial viscous damping and Fourier filtering are applied to simulate the physical Landau damping of short wavelength modes. Successive overrelaxation is employed for the calculation of the electrostatic potential when the density fluctuations are small. However, an asymmetric conjugate gradient method must be applied at high perturbation levels. Through a spectral analysis of many wavenumber modes after the saturation of the instability, the models appear to reproduce characteristic features of Type I spectral irregularities observed by radar and resolve a number of theoretical questions. In particular, it was found that (1) the phase velocity of dominant wavenumber modes tends to the acoustic velocity rather than to the electron drift velocity when quasilinear velocity reduction is allowed, and (2) the instability can establish a saturated state in less than a second. Assuming that the electrojet is turbulent on a scale of tens of meters or more, the isotropy of radar observations with respect to radar elevation angle is not inconsistent with the simulated results.

• Research Organization: Cornell Univ., Ithaca, NY (USA)
• OSTI ID: 6168167
• Country of Publication: United States
• Language: English

Related Subjects

640201* -- Atmospheric Physics-- Auroral
Ionospheric
& Magetospheric Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
CHARGED PARTICLES
CURRENTS
DAMPING
DIFFERENTIAL EQUATIONS
ELECTRIC CURRENTS
ELECTROJETS
ELECTRONS
ELEMENTARY PARTICLES
EQUATIONS
EQUATIONS OF MOTION
FERMIONS
GROWTH
INSTABILITY
IONS
LANDAU DAMPING
LEPTONS
MATHEMATICAL MODELS
MEASURING INSTRUMENTS
PARTIAL DIFFERENTIAL EQUATIONS
PHASE VELOCITY
PLASMA INSTABILITY
PLASMA MICROINSTABILITIES
RADAR
RANGE FINDERS
SATURATION
TWO-DIMENSIONAL CALCULATIONS
TWO-STREAM INSTABILITY
VELOCITY