THE EFFECT OF ARTIFICIAL MODIFICATION IN THE E-REGION ON HF RAY-PROPAGATION

During RF heating at 4.04 MHz an increase of 5 dB in the signal streng th of a 4.2 MHz probe wave has been observed. This is attributed to a heater induced increase in electron density in the E region leading to the opening up of a low angle propagation path from probe transmitter to receiver. The geometry of the experiment is consistent with an ele ctron density increase distributed in a torus in the E region centred above the heater site. (C) 1997 Elsevier Science Ltd.