| Improved Breakdown Characteristics in Vehicle Discharging Through Neutral Gas Release: Electrode Shaping and External Magnetic Fields |
05 NOV 1999 |
17 pages |
| Authors:
D. N. Walker; R. F. Fernsler; W. E. Amatucci; D. Duncan; M. J. Keskinen; NAVAL RESEARCH LAB WASHINGTON DC
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 | In earlier work we quantified the effect of the Mach number of neutral gas release and neutral gas species on minimum breakdown potential in ionospheric-like plasmas. The theoretical basis of this work incorporates the Townsend breakdown criterion to the ambient plasma to characterize the discharge. The results of a model based on this theory provide good agreement with the results of experiments in a variety ... |
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| The WIND-HAARP-HIPAS Interferometer Experiment |
22 APR 1999 |
12 pages |
| Authors:
P. Rodriguez; M. J. Keskinen; E. J. Kennedy; M. McCarrick; J. Preston; NAVAL RESEARCH LAB WASHINGTON DC PLASMA PHYSICS DIV
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| We report on the first experiment using two high power, high frequency transmitting facilities in a bistatic, interferometer mode. The HAARP and HIPAS facilities in Alaska radiated at 4525 kHz with total combined power of about 700 kW, in the direction of the WIND spacecraft. The WAVES experiment aboard WIND received the transmissions at a distance of about 25 earth radii. The experimental setup thus resembled Young's two-slit experiment. The ... |
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| The Effects of Neutral Gas Release on Vehicle Charging: Experiment and Theory |
30 OCT 1998 |
29 pages |
| Authors:
D. N. Walker; W. E. Amatucci; R. F. Fernsler; C. L. Siefring; M. J. Keskinen; NAVAL RESEARCH LAB WASHINGTON DC SPACEEXPERIMENT SECTION
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| This paper describes an experimental and theoretical research effort related to the mitigation of spacecraft charging by Neutral Gas Release (NGR). Laboratory simulations which employ a charged aluminum cylinder containing a neutral gas release valve have verified the effectiveness of NGR as a means of mitigating high voltages under environmental conditions close to the natural space environment. The charging electronics were developed under the Space ... |
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| Scaling Laws for the Spectrum of Interchange Instabilities in the High Latitude Ionosphere |
15 JUN 89 |
27 pages |
| Authors:
M. J. Keskinen; NAVAL RESEARCH LAB WASHINGTON DC
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| Constraints on and scaling laws associated with the power spectrum of interchange instabilities in the inertial regime in the high latitude ionosphere are derived using conservation laws implied by the fundamental nonlinear plasma fluid equations. Applications to large scale convecting high latitude ionospheric plasma density structures, patches, and enhancements are made. |
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| Stimulated Raman Scattering of Intense Laser Radiation in a Nuclear- Disturbed Space Plasma |
08 NOV 88 |
18 pages |
| Authors:
M. J. Keskinen; Y. C. Lee; NAVAL RESEARCH LAB WASHINGTON DC
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| Stimulated Raman scattering of intense laser radiation propagating in a nuclear-disturbed space plasma environment has been investigated. For parameters typical of a single high altitude nuclear explosion (HANE), we propagation due to Raman scattering, particularly for 10 micrometer radiation. 10 micrometer, respectively, and for beam power densities on the order of 100000 W/sq cm. Here gamma is the growth rate for simulated Raman scattering. For the multiple HANE case, approximate ... |
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| Effects of Ion Collisions on Quasilinear Heating by the Current-Driven Ion Cyclotron Instability in the High Latitude Ionosphere |
14 OCT 88 |
25 pages |
| Authors:
P. Satyanarayana; M. J. Keskinen; P. K. Chaturvedi; S. L. Ossakow; NAVAL RESEARCH LAB WASHINGTON DC
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| Using an effective relaxation time model, the effects of ion-ion and ion-neutral collisions on quasilinear ion heating by the current-driven ion cyclotron instability in the high latitude ionosphere have been studied. For conditions typical of the high latitude lower (200-300 km) F-region ionosphere, it is found that the combined effects of ion-neutral and ion-ion collisions tend to isotropize (S(tet)/T(par) approx. 1) the perpendicular T(per) and parallel S(tet) ion temperatures on ... |
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| Approximate Analytical Formulae for Electron Density and Collision Frequency in the Natural and Nuclear-Disturbed Ionosphere and Inner Magnetosphere |
22 FEB 88 |
27 pages |
| Authors:
M. J. Keskinen; J. A. Fedder; NAVAL RESEARCH LAB WASHINGTON DC
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| The phenomenological models of global electron density for the natural ionosphere of Ching and Chiu (1973) and Chiu (1975) have been extended to both lower (60 km) and higher (36,000 km) altitudes. Computer simulations of a high altitude nuclear explosion are analyzed to develop a phenomenological model of electron density. Approximate analytical formulae for electron density and associated electron collision frequency in both the natural and nuclear- distributed near earth ... |
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| Nonlinear Evolution of the Kelvin-Helmholtz Instability in the High Latitude Ionosphere |
21 DEC 87 |
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| Authors:
M. J. Keskinen; H. G. Mitchell; J. A. Fedder; P. Satyanarayana; S. T. Zalesak; NAVAL RESEARCH LAB WASHINGTON DC
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 | The nonlinear evolution of the electrostatic Kelvin Helmholtz instability, resulting from velocity-sheared plasma flows perpendicular to an ambient magnetic field, has been studied including Pedersen conductivity effects (i.e., ion-neutral collisions). The Kelvin Helmholtz instability develops in a distinctly different manner in the nonlinear regime with Pedersen coupling than without it. Specifically, the Pedersen coupling effects, in conjunction with a neutral wind and density gradient, (1) result in an increased time ... |
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| Spectral Characteristics of Interchange Turbulence in the Ionosphere |
22 OCT 86 |
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| Authors:
A. B. Hassam; W. Hall; J. D. Huba; M. J. Keskinen; SCIENCE APPLICATIONS INTERNATIONAL CORP MCLEAN VA
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| The spectral characteristics of turbulence associated with the magnetized plasma Rayleigh Taylor instability in the presence of a background neutral gas are studied. Particular attention is paid to comparing the spectra obtained in the ion neutral collision dominated case with the spectra from the ion inertia dominated case. A saturated level of turbulence is obtained for a model system confined between conducting boundaries with an imposed density gradient between the ... |
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| Magnetic Reconnection in Laser-Plasma Interactions in a Background Magnetic Field |
09 MAY 86 |
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| Authors:
M. J. Keskinen; NAVAL RESEARCH LAB WASHINGTON DC
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| For laser irradiances I in the ablative regime (I < or = 10 to the 14th power w/sq cm, focused on a small solid target it is shown that magnetic field-reversed configuration, defined by the laser-produced self-generated magnetic field an externally applied magnetic field perpendicular to the laser axis, are possible near the laser-target interaction region. Approximate conditions under which these field-reversed regions undergo driven reconnection are investigated. Magnetic reconnection ... |
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| Production and Control of Ion Cyclotron Instabilities in the High Latitude Ionosphere by High Power Radio Waves |
30 DEC 85 |
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| Authors:
P. K. Chaturvedi; M. J. Keskinen; S. L. Ossakow; NAVAL RESEARCH LAB WASHINGTON DC
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| The possible generation and suppression of ion cyclotron waves in a collisional plasma by external high power electromagnetic (EM) waves with frequency close to the local upper-hybrid frequency is considered. It is shown that the ion cyclotron instability can be destabilized or (stabilized) for omega(o) Omega(UH), where omega(o) is the pump frequency of the EM wave. The results are applied to naturally occurring ion cyclotron instabilities in the high latitude ... |
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| Theory of the Current-Driven Ion Cyclotron Instability in the Bottomside Ionosphere |
11 NOV 85 |
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| Authors:
P. Satyanarayana; P. K. Chaturvedi; M. J. Keskinen; J. D. Huba; S. L. Ossakow; NAVAL RESEARCH LAB WASHINGTON DC
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| A theory of the current-driven electrostatic ion cyclotron(EIC) instability in the collisional bottomside ionosphere is presented. It is found that the electron collisions are destabilizing and are crucial for the excitation of the EIC instability in the collisional bottomside ionosphere. Furthermore, the growth rates of the ion cyclotron instability in the bottomside ionosphere maximize for (K-perpendicular) (rho sub i) > or = 1 where 2 pi/K- perpendicular is the mode ... |
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| A Simulation of High Latitude F-Layer Instabilities in the Presence of Magnetosphere-Ionosphere Coupling |
08 JUL 85 |
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| Authors:
H. G. Mitchell Jr.; J. A. Fedder; M. J. Keskinen; S. T. Zalesak; NAVAL RESEARCH LAB WASHINGTON DC
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| A magnetic-field-line-integrated model of plasma interchange instabilities is developed for the high latitude ionosphere including magnetospheric coupling effects. We show that primary magnetosphere-ionosphere coupling effect is to incorporate the inertia of the magnetospheric plasma in the analysis. As a specific example, we present the first simulation of the E x B instability in the inertial regime, i.e., nu sub i > omega. Our results show that striations produced in the ... |
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| Ionospheric Turbulence: Interchange Instabilities and Chaotic Fluid Behavior |
22 NOV 1984 |
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| Authors:
J. D. Huba; A. B. Hassam; I. B. Schwartz; M. J. Keskinen; NAVAL RESEARCH LAB WASHINGTON DC
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| We develop a set of mode coupling equations which describe the nonlinear evolution of the Rayleigh-Taylor and E X B gradient drift instabilities which are relevant to the ionosphere. The model is restricted to 2D turbulence in the plane transverse to the magnetic field, and only those modes such that kL >> 1 are considered, where k is the wavenumber and L is the scale length of the density gradient. ... |
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| Nonlinear Theory of the E x B Instability with an Inhomogeneous Electric Field |
09 JAN 1984 |
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| Authors:
M. J. Keskinen; NAVAL RESEARCH LAB WASHINGTON DC
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| Using analytical and numerical techniques, the nonlinear evolution of the E x B instability with an inhomogeneous electric field has been studied. For the case where the electric field component parallel to the density gradient is inhomogeneous, the author finds that the inhomogenous E x B instability in the nonlinear regime (1) destabilizes short wavelength linear stable modes, (2) evolves into large scale anisotropic finger-like structures, (3) can be described ... |
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| Unified Theory of the Power Spectrum of Long Wavelength Ionospheric Electron Density Irregularities |
09 JAN 1984 |
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| Authors:
R. N. Sudan; M. J. Keskinen; NAVAL RESEARCH LAB WASHINGTON DC
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| An extension of the Kolmogorov theory of fluid turbulence is used to develop a unified treatment of the power spectrum of long wavelength electron density structures and irregularities in the equatorial and high latitude ionosphere. Favorable comparison is made among theory, experimental observations, and numerical simulations. (Author) |
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| Analytic Models of Magnetic Field Evolution in Laser-Produced Plasma Expansions |
31 AUG 1983 |
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| Authors:
M. J. Keskinen; NAVAL RESEARCH LAB WASHINGTON DC
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| Analytic models of the magnetic field evolution in laser-produced plasma expansions have been studied and applied to the NRL laser HANE (high altitude nuclear explosion) simulation experiment. Both one- and two-dimensional models have been investigated for laser plasma expansions with and without initial background magnetic fields. For the case with no initial background magnetic field, thermal source mechanisms have been used to discuss the two- dimensional evolution and morphology of ... |
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| Parametric Excitation and Suppression of Convective Plasma Instabilities in the High Latitude F-Region Ionosphere |
14 JUL 1983 |
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| Authors:
M. J. Keskinen; P. K. Chaturvedi; S. L. Ossakow; NAVAL RESEARCH LAB WASHINGTON DC
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| Parametric coupling processes of a large amplitude electromagnetic pump wave with convective plasma fluid instabilities (E X B gradient drift and current convective) in the high latitude F region ionosphere have been studied. We find that a pump wave, with frequency near the upper hybrid frequency and with electric field, can stabilize or destabilize the E X B gradient-drift and/ or current convective instability. For parameters typical of the nighttime ... |
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| Theories of High Latitude Ionospheric Irregularities: A Review |
17 NOV 1982 |
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| Authors:
M. J. Keskinen; S. L. Ossakow; NAVAL RESEARCH LAB WASHINGTON DC
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| We present, in this paper, an overview of theories of naturally occurring high latitude E and F region ionospheric irregularities. (For a review of artificially-induced irregularities, e.g., from ionospheric 'heating' experiments, see Fejer 1979.) Emphasis is placed on recent results, particularly with regard to sources of high latitude irregularities. Physical mechanisms are stressed with extensive mathematical analysis avoided. Expertise in plasma physics has not been assumed. We summarize the recent ... |
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| Electron Velocity Shear Instability in the Auroral Ionosphere |
25 JUN 1982 |
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| Authors:
M. J. Keskinen; J. D. Huba; NAVAL RESEARCH LAB WASHINGTON DC
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| A linear electrostatic kinetic theory of velocity sheared electron streams flowing parallel to the geomagnetic field is presented. Our development, which includes the effects of density gradients, background ions and electron collisions, is valid for arbitrary T sub e/T sub i, where T sub e and T sub i are the electron and ion temperatures, respectively. For applications to the auroral ionosphere, we find that the interface between downward flowing ... |
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| Nonlinear Evolution of Convecting Plasma Enhancements in the Auroral Ionosphere II. Small Scale Irregularities |
18 MAY 1982 |
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| Authors:
M. J. Keskinen; S. L. Ossakow; NAVAL RESEARCH LAB WASHINGTON DC
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| The linear stability and nonlinear evolution of small scale density irregularities in local unstable regions of large scale convecting auroral plasma enhancements have been studied using analytical and numerical simulation techniques. Our results show that these small scale size irregularities are driven unstable primarily by the effects of convection and field aligned currents. Furthermore, we find that the density irregularities, in the nonlinear regime, in a plane nearly perpendicular to ... |
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| Ionospheric Irregularity Physics Modelling |
09 FEB 1982 |
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| Authors:
S. L. Ossakow; M. J. Keskinen; S. T. Zalesak; NAVAL RESEARCH LAB WASHINGTON DC
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| Theoretical and numerical simulation techniques have been employed to study ionospheric F region plasma cloud striation phenomena, equatorial spread F phenomena, and high latitude diffuse auroral F region irregularity phenomena. Each of these phenomena can cause scintillation effects. The results and ideas from these studies are state-of-the-art, agree well with experimental observations, and have induced experimentalists to look for theoretically predicted results. One conclusion that can be drawn from these ... |
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| Nonlinear Evolution of Plasma Enhancements in the Auroral Ionosphere I: Long Wavelength Irregularities |
05 OCT 1981 |
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| Authors:
M. J. Keskinen; S. L. Ossakow; NAVAL RESEARCH LAB WASHINGTON DC
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| The linear stability and nonlinear evolution of plasma enhancements in arbitrary ambient electric fields in the diffuse auroral F region ionosphere have been studied using analytical and numerical simulation techniques. Our results that equatorward convecting plasma slabs initially limited in latitudinal extent are primarily destabilized on their poleward sides by a combination of the effects of convection and field aligned currents. Furthermore we find that the plasma enhancements break up ... |
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| A Plausible Hypothesis for Striation Freezing in Ionospheric Plasma Clouds |
18 AUG 1981 |
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| Authors:
S. L. Ossakow; S. T. Zalesak; M. J. Keskinen; NAVAL RESEARCH LAB WASHINGTON DC
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| Ionospheric plasma cloud striation phenomena exhibit a persistence of kilometer scale size structures, i.e., a freezing. Beyond a certain point in time the striations drift in unison without further bifurcation. Recent theoretical and nonlinear numerical simulation studies using a one level, 2D plasma cloud model with cross field diffusion produced a U shaped curve for minimum striation scale size, i.e., a structure's stability against further bifurcation, as a function of ... |
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| Nonlinear Stabilization of the Farley-Buneman Instability by Strong E x B Turbulence |
31 JUL 1981 |
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| Authors:
M. J. Keskinen; NAVAL RESEARCH LAB WASHINGTON DC
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| It is shown that through nonlinear mode coupling processes long wavelength low frequency strong E x B turbulence can stabilize short wavelength high frequency Farley-Buneman modes in a weakly ionized low pressure convecting plasma. Favorable comparisons are made with experimental observations. (Author) |
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| Effect of Different Initial Conditions on the Evolution of the E X B Gradient Drift Instability in Ionospheric Plasma Clouds. |
14 APR 1981 |
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| Authors:
M. J. Keskinen; S. L. Ossakow; NAVAL RESEARCH LAB WASHINGTON DC
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| Both small and large amplitude monochromatic (one wave) and random (many waves) initial perturbations have been used to seed initially slablike plasma clouds with different magnetic field line integrated Pedersen conductivity gradient scale lengths L = 4, 6, 10 km perpendicular to the magnetic field. Independent of the initial conditions used, all of the models studied become similar in the nonlinear late time regime both in real (x, y) space ... |
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| On the Spatial Power Spectrum of the E x B Gradient Drift Instability in Ionospheric Plasma Clouds. |
14 APR 1981 |
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| Authors:
M. J. Keskinen; S. L. Ossakow; NAVAL RESEARCH LAB WASHINGTON DC
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| It is shown that the two dimensional power law spatial power spectra of magnetic field line integrated Pedersen conductivity perturbations in the plane perpendicular to the magnetic field recently computed from numerical simulation studies of ionospheric plasma clouds are consistent with conservation laws implied by the fundamental plasma fluid equations describing the E X B gradient drift instability in these ionospheric plasma clouds. (Author) |
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| Nonlinear Theory and Experimental Observations of the Local Collisional Rayleigh-Taylor Instability in a Descending Equatorial Spread-F Ionosphere. |
08 JAN 1981 |
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| Authors:
M. J. Keskinen; E. P. Szuszczewicz; S. L. Ossakow; J. C. Holmes; NAVAL RESEARCH LAB WASHINGTON DC
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| The nonlinear evolution of the local collisional Rayleigh-Taylor instability in downward-moving equatorial F layers has been studied in a coordinated theoretical and experimental program dealing with actual conditions of bottomside spread F. For ambient bottomside electron density gradient scale lengths L=8 and 25 km, we find large percentage depletions and inverse power law spatial power spectra over the intermediate wavelength range wavelength=25 m-1 km. In addition we outline a nonlinear ... |
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| Nonlinear Evolution of Diffuse Auroral F Region Ionospheric Irregularities. |
02 JUL 1980 |
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| Authors:
M. J. Keskinen; S. L. Ossakow; B. E. McDonald; NAVAL RESEARCH LAB WASHINGTON DC
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| Numerical simulations of the nonlinear evolution of the current convective instability in the diffuse aurora have been performed for conditions typical of the nighttime high latitude F region. Our results show nearly field aligned plasma irregularities developing in regions of well-defined northward gradients of total electron content (TEC) and field-aligned diffuse auroral particle precipitation. In addition, we find equatorward movement of plasma enhancements and northward (poleward) movement of plasma depletions ... |
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| Recent Computational Studies of the Equatorial Electrojet. |
24 MAR 1980 |
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| Authors:
M. J. Keskinen; NAVAL RESEARCH LAB WASHINGTON DC
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| A brief review of recent computational studies of the E-region equatorial electrojet is presented. Agreement and discrepancies between numerical simulation studies and both theory and experiment are given. Some outstanding problems are identified and new experiments suggested. |
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| Preliminary Report of Numerical Simulation of Intermediate Wavelength ExB Gradient Drift Instability in Ionospheric Plasma Clouds. |
07 DEC 1979 |
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| Authors:
M. J. Keskinen; S. L. Ossakow; P. K. Chaturvedi; NAVAL RESEARCH LAB WASHINGTON DC
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| Two-dimensional numerical simulations of intermediate wavelength (100-1000m) ExB gradient-drift instability in local unstable regions of large F region ionospheric plasma clouds have been performed, using an initial one-dimensional (y), cloud geometry, for plasma cloud density gradient scale lengths L = 3, 6, 10 km. For conditions typical of 200 km barium releases, we find that linearly unstable modes saturate by nonlinear generation of linearly damped modes along the y-direction (parallel ... |
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| Preliminary Report of Numerical Simulations of Intermediate Wavelength Collisional Rayleigh-Taylor Instability in Equatorial Spread F. |
26 NOV 1979 |
27 pages |
| Authors:
M. J. Keskinen; S. L. Ossakow; P. K. Chaturvedi; NAVAL RESEARCH LAB WASHINGTON DC
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| Computer simulations of the intermediate wavelength (100-1000 m) collisional Rayleigh-Taylor instability have been performed using parameters typical of the post-sunset bottomside (300 km) equatorial F region ionosphere. For ambient electron density gradient scale lengths L = 5, 10, 15 km we find that the linearly unstable modes saturate by nonlinear generation of linearly damped vertical modes with the result that in the nonlinear regime power laws are observed in the ... |
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| Temporal and Spatial Power Spectrum Studies of Numerical Simulations of Type II Gradient Drift Irregularities in the Equatorial Electrojet, |
JUN 1978 |
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| Authors:
M. J. Keskinen; R. N. Sudan; R. L. Ferch; CORNELL UNIV ITHACA N Y LAB OF PLASMA STUDIES
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| Temporal and spatial power spectra from computer simulations of the equations modeling Type II irregularities in the equatorial electrojet are presented. The power spectra are computed using the code of Ferch and Sudan, averaging over times as long as 20 seconds. The dependence of the average frequencies and linewidths on wavelenght and angle from the electrojet drift is studied. The mean frequencies obtained agree well with linear theory except at ... |
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Reports by Author
