Ground-based observations of radio emissions near 2fce and 3fce in the auroral zone



Narrow band emissions at frequencies near twice and three times the ionospheric electron cyclotron frequency have been observed with a ground based receiver located at Two Rivers, Alaska (near Fairbanks). The emissions at twice the local ionospheric electron cyclotron frequency ( ≈ 2.50–2.80 MHz) appear similar in frequency, intensity, local time dependence, and temporal structure to auroral “roar” events previously observed at Churchill, Manitoba [Kellogg and Monson, 1979; 1984]. The observation of emissions near 3fce ( ≈ 3.66–4.24 MHz), sometimes observed simultaneously with the 2fce events, represents a new aspect of this phenomenon. A quantitative theoretical understanding of the phenomenon has not yet been achieved.