Harp Harmonics is a technique mostly used by classical guitarists, and is also often used with a clean tone, not a distorted one. What you do here is let the tip of your index finger touch the harmonic node while your right thumb strikes the string behind, setting the string in motion.
It is called Harp Harmonics simply because when using a clean sound, you get a harp-like effect when playing arpeggios in this fashion.
Classical musicians are also often MUCH better acquainted with the workings of harmonics, and are often aware that they can produce not only the octave tone by using Harp Harmonics, but any of the given harmonics on a string of choice.
I also present you with a variation on the technique, as used by Russian Balalaika artists. This involves allowing the side of the right hand thumb to touch the harmonic point while any finger of choice on the right hand strikes the string behind the thumb. I much prefer this method, since I do not have a long thumb nail, and I get a much cleaner and more effortless technique this way. Try it out, and see which one you prefer yourself!