APPLETON MAGNETO-IONIC THEORY AND THE LORENTZ POLARIZATION TERM

The historical developments and discoveries and the personal interactions which led Edward Appleton to demonstrate the existence of a reflecting layer in the upper atmosphere and consequently to formulate his magneto-ionic theory are described. His difference of opinion with D. R. Hartree concerning the inclusion of the Lorentz Polarisation is discussed and the subsequent efforts to resolve this problem by both experiment and theoretical arguments are outlined. It is concluded that 65 yr after Appleton first formulated his magneto-ionic theory, there is still some controversy regarding the Lorentz Polarisation Term and radiowave propagation in a plasma.