Bifurcation structure in Auroral radio emissions

The northern lights, or aurora borealis, are best known for the beautiful optical displays they present in the polar atmosphere. It is less widely known, but the northern lights also emit various types of radio waves which cannot be seen but can be detected with sensitive instruments. These radio waves provide insights into the physics of the aurora. One type of auroral radio emission, called auroral roar occurs on frequencies near 3 MHz, somewhat above the highest AM radio frequencies. On some occasions, this radio emission occurs on two closely space frequencies rather than a single frequency band, a phenomenon called a doublet structure. The explanation for these doublet structures is not known. The structure of the electron density in the ionosphere may play a role. The WISP project would entail cataloguing a large number of examples for the first time, in order to determine the distributions of the frequencies and the gap between them. This information may provide a test of whether ionospheric density structure can explain the phenomenon.https://digitalcommons.dartmouth.edu/wetterhahn_2023/1013/thumbnail.jp