U.S. Naval Research Laboratory research physicists and engineers from the Plasma Physics Division, working at the High-frequency Active Auroral Research Program (HAARP) transmitter facility, Gakona, Alaska, successfully produced a sustained high density plasma cloud in Earth's upper atmosphere.
"Previous artificial plasma density clouds have lifetimes of only ten minutes or less," said Paul Bernhardt, Ph.D., NRL Space Use and Plasma Section. "This higher density plasma 'ball' was sustained over one hour by the HAARP transmissions and was extinguished only after termination of the HAARP radio beam."
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Using the 3.6-megawatt high-frequency (HF) HAARP transmitter, the plasma clouds, or balls of plasma, are being studied for use as artificial mirrors at altitudes 50 kilometers below the natural ionosphere and are to be used for reflection of HF radar and communications signals.
Full article:
http://www.spacedaily.com/reports/NRL_Scientists_Produce_Densest_Artificial_Ionospheric_Plasma_Clouds_Using_HAARP_999.html