The High Frequency Active Auroral Research Program (HAARP) is an investigation project to “understand, simulate and control ionospheric processes that might alter the performance of communication and surveillance systems.” Started in 1993, the project is proposed to last for a period of twenty years.
The project is jointly funded by the United States Air Force, the Navy, and the University of Alaska. Defense Advanced Research Projects Agency (DARPA). Apart from its unusually high power capacity, it is said that the project is similar to numerous existing ionospheric heaters around the world, and has a large suite of diagnostic instruments that facilitate its use to increase scientific understanding of ionospheric dynamics. Although fears have been expressed that HAARP could be used as a nefarious global weapon, scientists involved in aeronomy, space science, or plasma physics say these fears are unfounded.
HAARP’s field of antennas search the stratosphere.
If radio transmissions are long and powerful enough, the beams actually change the distribution of electrons in the ionosphere, altering for a brief time literally the way the sky is put together.
Comparison of the HAARP with other ionospheric facilities
(From the HAARP website, public use permitted if source cited)