Investigation of the Stimulation of ULF Waves,
NAVAL RESEARCH LAB WASHINGTON D C
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Two methods of artificially stimulating ultra-low-frequency ULF waves in the ionosphere have been investigated experimentally. Radio-frequency heating of the ionospheric-dynamo-current region has been attempted using a high-frequency transmitter and has been found to be ineffective. Pulse modulation of the U.S. Navy VLF transmitter at Cutler, Maine, has been explored as a means of stimulating geomagnetic micropulsations. In a month-long experiment the transmitter was square-wave modulated at frequencies of 0.2, 1, and 5 Hz, with a network of sensitive magnetometers employed as micropulsation detectors. Though the experimental results are not statistically conclusive, micropulsations occurred on several occasions at harmonics of the transmitter modulation frequency. It is likely that ULF waves may be stimulated by this means under magnetically quiet conditions immediately following geomagnetically active days. It is concluded that practical means of emitting ULF waves for global communications are prohibitively expensive by comparison to other alternatives in the extremely-low-frequency or higher bands.
- Radiofrequency Wave Propagation
- Radio Communications