Generation of ELF and VLF waves by modulated HF heating of the polar electrojet

Modulated heating of the lower ionosphere, with modulation frequencies in the ELF and VLF range, gives rise to a corresponding modulation of the electron temperature and, thus, of the electrical conductivity. If a polar electrojet current exists, the current density is modulated, and an ELF or VLF signal is generated. Experiments were performed to test this mechanism, using the new ionospheric heating facility at Ramfjordmoen, Norway. It was found that this mechanism is sensitive in the full ELF range and for VLF frequencies exceeding 7 kHz, the upper limit of the VLF receiver used.