THE HELIOSPHERIC CAVITY RADIO-EMISSION - GENERATION OF DISCRETE TONESBY FERMI ACCELERATION VIA OSCILLATING BOUNDARY

A theory is presented that describes the formation of the discrete rad io tones that could apply to the radio emission observed in the outer heliosphere by the Voyager spacecraft. Specifically, a broadband emiss ion is assumed to be trapped within the heliospheric cavity. If the he liospheric outer boundary, the heliopause, has a large-scale, monochro matic oscillation, the trapped emission will form intense, discrete to nes at wave frequencies where the photon travel time is an integer rat io of the boundary oscillation period. A new set of nonlinear coupled difference equations am presented that describe the interaction of the trapped photon with the boundary, the set appearing similar to that u sed to model Fermi acceleration of particles via oscillatory boundarie s. Results indicate that heliopause oscillation periods on the order o f 1000s of seconds could generate tones at frequencies near those obse rved by Voyager. The tones can also drift in association with the chan ging cavity size or oscillation period.