Doppler-shifted cyclotron radiation from electrons: A theory of very low frequency emissions from the exosphere

Cyclotron radiation from electrons in the exosphere spiraling along a line of force away from the observer will appear at a frequency less than the local gyrofrequency. An electron traveling from the observer's hemisphere to the opposite hemisphere will radiate a decreasing frequency until it crosses the equator, and thence an increasing frequency. Propagation conditions and various particle speeds give frequency-time spectra similar to those observed. A method of scaling electron speeds and the field lines in which they occur from observed data is described. Tests of the theory are discussed.