High-frequency Active Auroral Research Program

The High-frequency Active Auroral Research Program is a University of Alaska Fairbanks program which researches the ionosphere – the highest, ionized part of Earth's atmosphere.

The most prominent instrument at HAARP is the Ionospheric Research Instrument, a high-power radio frequency transmitter facility operating in the high frequency band. The IRI is used to temporarily excite a limited area of the ionosphere. Other instruments, such as a VHF and a UHF radar, a fluxgate magnetometer, a digisonde, and an induction magnetometer, are used to study the physical processes that occur in the excited region.

Initially HAARP was jointly funded by the U.S. Air Force, the U.S. Navy, the University of Alaska Fairbanks, and the Defense Advanced Research Projects Agency.