High Frequency Active Auroral Research Program. A research program that created an ionospheric heater made of an array of three hundred antennas able to beam high-frequency radio waves into the sky, which, by heating up the ionosphere, could create an artificial aurora borealis. Unlike its natural counterpart, which mostly appeared at nighttime, the HAARP-created aurora borealis was generated during the daytime, as the ionosphere disappeared at night.