Nc. Rogers et al., LARGE HF BEARING ERRORS FOR PROPAGATION PATHS TANGENTIAL TO AURORAL OVAL, IEE proceedings. Microwaves, antennas and propagation, 144(2), 1997, pp. 91-96
Large electron density gradients in the ionosphere associated with the
walls of the midlatitude trough produce tilted reflecting surfaces wh
ich lead to HF signals propagating over paths well displaced from the
great circle. Measurements are presented of signals propagating over t
wo paths along the midlatitude trough for which bearings deviations of
up to 100 degrees from the great-circle path, i.e. the expected direc
tion of arrival, were frequently recorded. The times of occurrence and
magnitude of these large deviations are consistent with the known fea
tures of the midlatitude ionospheric trough. Such large deviations of
the measured bearing from the great-circle path, which far exceed the
instrumental errors, have serious implications for the operation of po
sition location systems operating within the HF band.