The High-frequency Active Auroral Research Program (HAARP) located in Gakona, Alaska, is centered around the Ionospheric Research Instrument (IRI), a high-power, high-frequency phased array radio transmitter with 180 antennas used to temporarily excite a portion of the ionosphere. Studies of these disturbances can provide insights into natural ionospheric processes and solar-terrestrial interactions1. The IRI operates on frequencies from 2.7 to 10 MHz and can transmit in continuous or pulsed waves, the latter being used as a radar system to measure the decay of ionospheric modifications1.
The HAARP facility also includes a fluxgate magnetometer, a digisonde for ionospheric profiling, and an induction magnetometer to measure geomagnetic fields1. It was constructed in three phases, with the final phase completed in 2007, allowing the array to theoretically reach a maximum effective radiated power (ERP) of 5.1 gigawatts1. Located north of Gakona, near Wrangell-Saint Elias National Park, HAARP was built on the site of a former over-the-horizon radar installation1.
