Modeling of the ambient and disturbed ionosphere media pertinent to ELF/VLF propagation

The ion and electron concentration and the electrical conductivity in the ionospheric media during ambient and solar disturbance periods was modelled. Solar particle events (SPE) ranging from moderate to intense in magnitude and differing in spectral hardness are modelled to define the source terms and sometimes electron density profiles. It is shown that during intense SPE's the conductivity at 40 km can be increased over 200 times. The principal ELF attenuation occurs near the bottom of the ionosphere at 20 to 40 km. A secondary loss occurs near the top of the ionosphere due to ohmic dissipation with enhanced electron density. It is concluded that ionospheric modelling provides the basis for experiments with ELF propagation under solar particle disturbed conditions.