GENERATION OF ELF/VLF WAVES WITH MULTIPLE-SITE EXCITATION
- GENERATION OF VLF WAVES IN THE IONOSPHERE WITH CO-HERENT
HIPAS and HAARP are two radiating facilities in the Arctic region.
The distance between these two radiating facilities is 287 km, which
is on the order of the ELF/VLF wavelengths. The electrojet in the E
region of the ionosphere above each facility can be modulated to
radiate ELF/VLF waves via HF heating.
These two facilities are link together to transmit HF heating power
in a manner that can enhance the efficiency of excitation of ELF/VLF
by both low frequency modulations and high frequency beam
interactions. The electrojet radiates electromagnetic waves at its
modulation frequency in the ELF/VLF band and thus becomes a wave
source. When both HIPAS and HAARP are radiating with amplitude
modulation (AM) at the same ELF/VLF frequency, the wave sources
formed above the two sites become coherent.
Coherent excitations by these two facilities can create constructive
interference which is sensitive to the phase difference between these
two sources. Density irregularities, or striations, generated by high
power radio frequency heating, can be modeled as a vertical
conducting surface in ionospheric region directly above each
Since a conducting surface reflects electromagnetic waves, ELF/VLF
waves will be reflected and will propagate within the ionospheric
region between HIPAS and HAARP in a manner dependant upon the
reflection coefficient of the surfaces. The multiple reflections
between these two wave sources above HIPAS and HAARP create the
equivalent of a large antenna source for ELF/VLF signals.
Generalization of this result to N sites for ELF/VLF excitation could
imply that it is more advantageous to distribute a given amount of
power among N sites as opposed to a single site concentration.