Cyclotron maser

Among these, gyrotrons and cyclotron resonance masers are high-frequency vacuum electronic devices that have the ability to produce sufficient power in the frequency range of 140-590 GHz for electrons (200-900 MHz for proton nuclei). The electron cyclotron resonance maser can emit the coherent radiation near the relativistic electron cyclotron frequency. The irradiation frequency is given by... 

Most of the emissions were polarized and probably due to maser-cyclotron emission. The emissions range in frequency from about 20 kHz to 800 kHz, well below the frequency range that is observable from the Earth. The emissions suggest a magnetosphere rich in magnetohy-drodynamic phenomena. 

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