Z mode radio sounding from IMAGE of field aligned electron density and ducts

Radio sounding from IMAGE has led to the observations of a large variety of ducted and nonducted fast Z mode echoes. The ducted echoes were observed when IMAGE was located inside a Z mode “cavity,” whereas the nonducted echoes were observed both inside and outside of the cavity. We present a new ray tracing method to measure field aligned electron density and duct and Z mode cavity parameters from the observed cutoff frequencies and dispersion of the ducted and nonducted fast Z mode echoes. The method is applied to four case studies to obtain field aligned electron densities and duct parameters. Our results demonstrate that Z mode radio sounding observations from IMAGE provide a powerful new way to measure field aligned electron density and duct parameters that play important roles in the physics of whistler and Z mode wave propagation, wave particle interactions, and that of ionosphere magnetosphere coupling.