THE EFFECTS OF POWERFUL OBLIQUE RADIO TRANSMISSION ON THE IONOSPHERE ON VERTICAL SOUNDING DATA

Results of experiments measuring the effects of a powerful oblique HF radio transmission on the ionosphere are described. In one experiment carried out in 1991 on a longitudinal path in the south-west part of t he U.S.A., additional traces were found on vertical sounding (VS) iono grams generated by an ionosonde located near the mid-point of the path . Numerical synthesis of VS ionograms using reasonable ionospheric mod els produce additional traces showing that they can be formed by a lar ge scale inhomogeneity of electron density that is produced by a power ful HF transmitter. This inhomogeniety appears in a region of the caus tic wedge. These extra traces can be caused either by enhanced or depl eted electron densities, although the characteristics associated with each is different. The negative (depleted) disturbance, stretched alon g the interior branch of the caustic, gives a more adequate descriptio n of the observed effects. (C) 1997 Elsevier Science Ltd.