Long-range detection of VLF radiation produced by heating the auroral electrojet

This paper presents the first evidence of long-range detection (>1000 km) of calibrated VLF signals resulting from the HF heating of the auroral electrojet, that is, signal detection at a point of direct “line of sight” of the heated patch of ionosphere. Other workers have presented calibrated data from shorter ranges (190-550 km) or claimed the detection of uncalibrated signals at ranges greater than 6000 km, but we believe that no such calibrated and clear signals, like those presented here from a range of greater than 2000 km, have previously been reported. Also, in contrast to earlier long-range detection experiments we record the “radial” as well as the “azimuthal” magnetic component of the signals and from their ratio obtain the waveguide mode polarization. Observed absolute magnetic field strengths and waveguide polarizations are found to be in line with the predictions of simple waveguide models.