An improved whistler-mode refractive index equation

Introduction. The Appleton-Hartree equation is often approximated for computational and conceptual purposes. Most often used, and the most valuable of these approximations, is the quasi-longitudinal (QL) [Booker, 1935]. We propose here a modification of this approximation for the whistler mode which results in the correct location of the refractive index infinity and a closer approximation to the position of the points of inflection.