The reception of whistler mode signals at a point remote from the transmitter's magnetic conjugate point

Abstract

An attempt is made to describe the propagation characteristics of a whistler mode radio signal over the complete one-hop path from a transmitter to a receiver that is up to several thousand kilometers away from the transmitter's magnetic conjugate point. It is shown that there are likely to be two preferred propagation paths with less total transmission loss than for other possible paths: (1) under the ionosphere from the transmitter to the receiver's conjugate point, then along a magnetospheric path to the receiver; (2) along a magnetospheric path from the transmitter to its conjugate point, then under the ionosphere to the receiver. A long series of observations of whistler mode signals from station NPG, near Seattle, on 18.6 kc/s, received near Wellington, New Zealand, 2570 km from the Vestine conjugate of NPG, using three different methods, gave results that are in accord with the idea of two preferred paths. More recent observations of 24.0-kc/s transmissions from the same station also gave general support to this idea.