Date of Award


Degree Type


Degree Name

Doctor of Philosophy


It is commonly accepted in the literature that the phase speed of Farley-Buneman waves in the E-region electrojets saturates at approximately the instability threshold phase speed (or ion-acoustic speed) of traditional linear theory. The formula often quoted, viz{dollar}{dollar}C\sbsp{lcub}s{rcub}{lcub}2{rcub} = {lcub}\gamma\sb{lcub}i{rcub}T\sb{lcub}i{rcub}+\gamma\sb{lcub}e{rcub}T\sb{lcub}e{rcub}\over m\sb{lcub}i{rcub}{rcub},{dollar}{dollar}customarily assumes isothermal behaviour({dollar}\gamma\sb{lcub}e,i{rcub} = 1),{dollar} or adiabatic behaviour ({dollar}\gamma\sb{lcub}e,i{rcub} = 5/3{dollar}) for the electrons and ions. As neither assumption is true in general, we have improved the traditional approach by including the effects of electron energy exchange and heat flow through the use of Grad's 8-moment method, with collision terms derived from the Boltzmann collision integral. The ions are treated in the traditional isothermal way.;Within this framework, a Generalized local, linear, fluid Dispersion Relation (GDR) for Farley-Buneman waves has been derived. From the GDR, equations for {dollar}C\sbsp{lcub}s{rcub}{lcub}2{rcub},\gamma\sb{lcub}e{rcub},{dollar} the threshold electron drift velocity and growth rate {dollar}\Gamma{dollar} have been investigated analytically and traditional limits recaptured. In the absence of energy exchange effects it is found that (a) thermal force and thermoelectric effects can alter significantly the expression for {dollar}\gamma\sb{lcub}e{rcub},{dollar} leading to values as high as 5/2 in the fluid regime for a hard sphere interaction; (b) the aspect angle limitation on wave propagation is only slightly affected; and (c) in the fluid limit, the instability is still of a modified two-stream nature.;Preliminary investigations have suggested that energy exchange effects might be of great importance in the long wavelength limit, although further research is required.



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