Modification of Ionospheric Conductance by Wave Effects, and an Electromagnetic Model

Abstract:

An electromagnetic model has been developed for the ionosphere and used to study the ionospheric conductance. The model is developed from an exact linearization of the electromagnetic 5-moment fluid equations, writing down the integral form of the driven steady state solution, and approximating the integrands with analytic functions. This yields a solution valid for homogeneous plasma, expressed as a sum over modal contributions associated with the eigenvectors/eigenvalues of the electromagnetic 5-moment fluid equations, which we find numerically. Transmission line theory is used to extend the homogeneous-plasma solution to a one-dimensional model for the vertically stratified ionosphere using two wave modes, the Alfvén wave and the Whistler wave. The use of two wave modes is justified by analyzing the complete set of modes in the homogeneous-plasma solution to find which are capable of transmitting energy through the ionosphere, based on characteristic ranges of spatial and temporal scale. The model reproduces electrostatic theory quite closely for low density, thin plasma layers at short transverse wavelengths. However, at higher densities and longer transverse wavelengths, effects from short parallel wavelengths and mode mixing begin to dominate. There appears to be a wide range of parameter space where electrostatic theory does not accurately describe the ionospheric conductance, including an important parameter range where it is simply inapplicable, owing to profound short-wavelength effects.