Imposing less stringent restrictions than in the case of quasielectrostatic theory, we have derived the expressions for the wave refractive index N which appeared in most cases to be close to the corresponding quasielectrostatic expressions derived in our previous papers. It is pointed out that the quasielectrostatic approximation can be insufficient for wave normal angles θ close to that at which dN dθ → ∞. © 1988.
Sazhin, S. S. (1988). An improved quasielectrostatic approximation. Planetary and Space Science, 36(2), 123–124. https://doi.org/10.1016/0032-0633(88)90048-7