Abstract

Many natural ionospheric irregularities are capable of focusing radio energy into very small volumes. In the presence of such irregularities a megawatt transmitter might be expected to produce a quasi-random distribution of small, intensely heated regions in the ionosphere, rather than the more uniform distribution of energy predicted for ‘smooth’ ionospheres. Rapid electron diffusion up and down the magnetic lines of force from the heated regions would cause ionization depletions, which would further enhance the radio focusing and in effect ‘amplify’ the original irregularities. The end result would be the growth of many small but intense field-aligned irregularities of the type known to cause at least one type of ‘spread-F’ ionosonde echo [Bowman, I960].