Triggered Auroral Kilometric Radiation

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9312013 Calvert Auroral electron precipitation is hypothesized to result from electron pitch-angle scattering by the cyclotron maser instability during the generation of auroral kilometric radiation (AKR). The AKR consists of intense, primarily extraordinary-mode waves originating on auroral magnetic field lines at geocentric altitudes of 1.3 to 3.3 earth radii. Comprising up to one percent of the total power of the aurora the AKR is now widely believed to be generated by the cyclotron maser instability which results from the doppler-shifted, cyclotron-resonant, pitch-angle scattering of energetic electrons into the loss cone. Critical to this new theory of the aurora is explaining the observed triggering of the AKR by radio waves from the sun, since that phenomenon clearly confirms the new theory. The proposed work is to study this triggering, believed to be caused by enhanced local precipitation in ambient density minima and the consequent creation of density depletions in which radio lasing can occur. Such radio lasing consists of closed-loop wave feedback oscillations caused by wave reflections at the source, exactly analogous to those of conventional optical lasers and likewise producing nearly-perfect discrete, coherent, and monochromatic emissions. ***