Effects of density gradients on the growth and damping of electrostatic electron cyclotron harmonic waves

The HOTRAY ray tracing code is used to study the refraction of electrostatic waves into Z mode radiation, and to calculate the path integrated growth rate. A plasma density model is constructed from DE 1 wave data during an event where (n + 0.5)f(ce) waves were detected at the magnetic equator, and where terrestrial myriametric radiation (TMR) was detected just a few degrees north and south of the equator. The distribution consists of one cold component and one hot loss cone component. Ray tracing shows that backward propagating electrostatic waves can refract into forward propagating waves, and then into electromagnetic Z mode radiation which can propagate to the radio window. The waves are amplified by the loss cone by a a factor of 42. Increasing the depth of the loss cone or the hot plasma density to within observed limits increases the amplification up to a factor of 10,000. Since the linear mode conversion window theory for the generation of TMR only requires an amplification factor above 20, these results provide strong support for the theory.

Details