On VLF radiation fields along the static magnetic field from sources immersed in a magnetoplasma

The focusing of waves from radiating VLF sources immersed in a cold magnetoplasma is investigated for the case in which the focusing takes place along the static magnetic field direction. The explicit form of tensor Green´s function valid along the field line is derived for the far field, and the frequency ranges where focusing may be expected are specified. The theory is applied to calculate the power flux along the field line for an electric dipole and a magnetic loop with two orientations with respect to the static magnetic field.