Small-scale fluctuations in D-region ionization due to hydrodynamic turbulence

Hill, Reginald James

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https://hdl.handle.net/2142/25643 Copy

Description

Title

Small-scale fluctuations in D-region ionization due to hydrodynamic turbulence

Author(s)

Hill, Reginald James

Issue Date

1977

Doctoral Committee Chair(s)

Bowhill, S.A.

Department of Study

Physics

Discipline

Physics

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• D-region ionization
• hydrodynamic turbulence
• atmospheric turbulence
• plasma dynamics
• turbulent advection

Language

en

Abstract

The fluctuations at small length scales in V-region ionization caused by atmospheric turbulence are investigated. Consideration is given to the dynamics of the plasma, the statistical theory of turbulent advection, the relaxation to photochemical equilibrium, and the theoretical prediction of observed scattered power from electron-concentration fluctuations. The electron-neutral and ion-neutral collision frequencies for usc in the continuum momentum equation are determined for low-frequency phenomena in the lower ionosphere. It is found that the assumption of a displaced Maxwellian distribution function is not a good approximation for determining such electron-neutral momentum transfer collision frequencies. Those collision frequencies which yield transport coefficients in agreement with kinetic theory arc determined. A new equation is derived for the drift, distortion and diffusion relative to the neutral gas of ionization inhomogeneities in the presence of both uniform and turbulent motion of the neutral gas with uniform magnetic and gravitational fields. New effects are found which are due to the production of ionization inhomogeneities by the accelerations of the neutral gas and -to the coupling of the fluxes of charged particles with the spatial derivations of velocity of the neutral gas. The implications of the magnetic field effects on the diffusion, drift, distortion and production of ionizatioll inhomogeneities are considered quantitatively for D-region conditions. A theory is developed for ambipolar diffusion in a multiconstituent weakly-ionized plasma. The implications of the presence of negative ions and of differing positive-ion and negative-ion diffusion coefficients are found. In particular, the presence of numerous negative ions is found to enhance the diffusion of the electrons. Furthermore, this theory of multi-constituent ambipolar diffusion is extended to include the non-neutral case in which the length scale of the inhomogeneity is smaller than, or on the order of, the electron Debye length. A general treatment is derived for the modes of response of a multi-constituent, magnetic-field-free, weakly-ionized plasma for arbitrary numbers of different ionic species. This unified development reveals the interrelationship for D-region conditions of the multiconstituent diffusion modes with such phenomena as the collisional damping of ionic' and electron fluid velocities, free-electron diffusion, overdamped and underdamped space charge waves, and thermal-relaxation effects. The relaxation to photochemical equilibrium within displaced air parcels is investigated for the D region. In the upper D region the photochemistry of electrons, nitric oxide and NO+ is considered. For the lower D region a two-negative-ion model is used and the effects of time-dependent atomic- oxygen, ozone and Delta2(1Deltag) concentrations are considered. Analytic solutions for the concentrations are obtained over a wide range of time scales extending from detachment-attachment times to recombination time scales. The statistical theory of turbulence is considered and a model for the scalar spectrum is developed which is valid for arbitrary ratio of kinematic viscosity to diffusivity. The model is shown to yield good comparison with data from oceanic and lower-atmospheric turbulent advection. The cross section per unit volume for scattering of ratio waves from fluctuations in the electron concentration is expressed in terms of the model spectrum and the sensitivity of scattered power to changes in the energy dissipation rate in diffusive ranges is demonstrated. Using the knowledge of diffusive processes in the D region the parameters which govern the altitude dependence of backscattered power are given. The cross section per unit volume and its variations are estimated from observations of the backscattered power and shown to be consistent with the model spectrum.

Type of Resource

text

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http://hdl.handle.net/2142/25643

Copyright and License Information

1977 Reginald James Hill

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