“…Radio propagation is powerful probe of the density distribution of magnetospheric and ionospheric plasma. The refractive, diffractive and dispersive effects that free electrons have on radio signals enable structure to be deduced from whistler spectrograms [Sagredo and Bullough, 1973;Singh et al, 1994], observations of cosmic radio sources [Wild and Roberts, 1956;Coker et al, 2009;Helmboldt and Intema, 2014;Loi et al, 2015a], sounding and radar scattering experiments [Hunsucker , 1991], and satellite dual-frequency delay measurements [Mannucci et al, 1998;Bernhardt and Siefring, 2006;Hawarey, 2006]. The geomagnetic field imposes significant anisotropy in the shapes of density irregularities, since electron and ion mobilities are much larger parallel than perpendicular to the magnetic field [Calvert and Warnock , 1969;Booker , 1979].…”