spaceweb@oulu.fi - last update: 2 December 1998, 1000 UT (RR) . Auroral kilometric radiation (AKR) is bursty electromagnetic emission at about 100 - 500 kHz related to auroral arcs , i.e., dusk and evening side discrete auroras. ... The source region altitude is about 3000 - 20000 km; however, at a given time only a small altitude range is operational. ... It is composed of both extraordinary and ordinary modes, with the extraordinary mode dominating. ... 1989). ... 94 , 6643-6654, 1989. ...