61 research outputs found

    A Simulation of High Latitude F-Layer Instabilities in the Presence of Magnetosphere-Ionosphere Coupling

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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 where nu sub i is the ion-neutral collision frequency and omega is the wave frequency. We find that the inertial E x B instability develops in a fundamentally different manner than in the collisional case ni sub i omega. Our results show that striations produced in the inertial regime are spread and retarded by ion inertial effects, and result in more isotropic irregularities than those seen in the collisional case

    Modeling High Altitude Electron Density Plumes Using Direct Numerical Simulation

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    Electron densities form field-aligned structured regions in the natural ionosphere and after a high altitude nuclear explosion (HANE). These electron densities, known as plumes, are made up of many smaller individual field-aligned regions called striations. Striation modeling for systems effects has traditionally been done use a statistical approach. This statistical approach evolves different moments of the electron density. Due to lack of test data it has never been validated. The purpose of this project was to use a direct numerical simulation to solve equations governing the differential motion of individual striations. It was done in five steps: 1) Transport a single striation, 2) solve potential equation, 3) combine transport and potential equations, 4) optimize combined solver, and 4) simulate a fully-striated plume for comparison with the statistical model

    Ionosphere/microwave beam interaction study

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    A solar power satellite microwave power density of 20mw sq cm was confirmed as the level where nonlinear interactions may occur in the ionosphere, particularly at 100 km altitude. Radio wave heating at this altitude, produced at the Arecibo Observatory, yielded negative results for radio wave heating of an underdense ionosphere. Overdense heating produced striations in the ionosphere which may cause severe radio frequency interference problems under certain conditions. The effects of thermal self-focusing are shown to be limited severely geographically. The aspect sensitivity of field-aligned striations makes interference-free regions above magnetic latitude about 60 deg. A test program is proposed to simulate the interaction of the SPS beam with the ionosphere, to measure the effects of the interaction on the ionosphere and on communication and navigation systems, and to interpret the results

    Analysis of optical observations and three-dimensional hybrid code simulation of the CRRES plasma injection experiments in space

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    Thesis (Ph.D.) University of Alaska Fairbanks, 1998The Combined Release and Radiation Effects Satellite (CRRES) was a NASA funded campaign designed to study a variety of plasma processes in the Earth's space environment. An analysis of optical data from three CRRES plasma injection experiments, in conjunction with results from a three-dimensional hybrid code simulation, have provided new insights into small-scale coupling processes in the ionosphere. The results have direct application to auroral processes, comets, and other similar geophysical/astrophysical systems

    An asymptotic preserving scheme for strongly anisotropic elliptic problems

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    In this article we introduce an asymptotic preserving scheme designed to compute the solution of a two dimensional elliptic equation presenting large anisotropies. We focus on an anisotropy aligned with one direction, the dominant part of the elliptic operator being supplemented with Neumann boundary conditions. A new scheme is introduced which allows an accurate resolution of this elliptic equation for an arbitrary anisotropy ratio.Comment: 21 page

    Effcient numerical methods for strongly anisotropic elliptic equations

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    In this paper, we study an effcient numerical scheme for a strongly anisotropic elliptic problem which arises in the modeling of ionospheric plasma dynamics. A small parameter \varepsilon induces the anisotropy of the problem, which leads to severe numerical diffculties for 0 < \varepsilo

    Electrodynamics of the plasma environment induced around spacecraft in low earth orbit : three-dimensional theory and numerical modeling

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    Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1991.Includes bibliographical references (leaves 226-236).by Nikolaos Achilleas Gatsonis.Ph.D

    Feedback instability in the magnetosphere-ionosphere coupling system: Revisited

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    A coupled set of the reduced magnetohydrodynamic and the two-fluid equations is applied to themagnetosphere-ionosphere (M-I) feedback interactions in relation to growth of quite auroral arcs. A theoretical analysis revisiting the linear feedback instability reveals asymptotic behaviors of the dispersion relation and a non-Hermite property in the M-I coupling. A nonlinear simulation of the feedback instability in the M-I coupling system manifests growth of the Kelvin?Helmholtz-like mode in the magnetosphere as the secondary instability. The distorted vortex and field-aligned current profiles propagating as the shear Alfv?n waves lead to spontaneous deformation of ionospheric density and current structures associated with auroral arcs

    Weakly nonlinear ion waves in striated electron temperatures

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    The existence of low-frequency waveguide modes of electrostatic ion acoustic waves is demonstrated in magnetized plasmas for cases where the electron temperature is striated along magnetic field lines. For low frequencies, the temperature striation acts as waveguide that supports a trapped mode. For conditions where the ion cyclotron frequency is below the ion plasma frequency we find a dispersion relation having also a radiative frequency band, where waves can escape from the striation. Arguments for the formation and propagation of an equivalent of electrostatic shocks are presented and demonstrated numerically for these conditions. The shock represents here a balance between an external energy input maintained by ion injection and a dissipation mechanism in the form of energy leakage of the harmonics generated by nonlinear wave steepening. This is a reversible form for energy loss that can replace the time-irreversible losses in a standard Burgers equation
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