Type I Radio Bursts Deflected by Lower Hybrid Waves

Abstract

What are the observational effects if type I bursts are deflected by lower-hybrid waves? The deflection creates an elliptical radio mirage, with the direct source at one end of the minor axis. Unlike a ‘scattering disk’, the mirage has considerable polarization structure which should be observable at high angular resolution. The lower-hybrid waves have four attractive features to explain existing observations of type I bursts: they naturally yield zero polarization for limb bursts; they preserve a high directivity even for limb bursts; they can explain the observed constancy of polarization during partially polarized bursts; and they depolarize at a sufficient height so that the resulting two circular polarizations arrive nearly simultaneously, as observed. The small time interval between the arrival of the two polarizations requires that we normally observe only the mirage and that the source be asymmetric with respect to azimuth around the magnetic field. The waves appear to be restricted to the vicinity of type I sources.