HF wave propagation and induced ionospheric turbulence in the magnetic equatorial region

The propagation and excitation of Artificial Ionospheric Turbulence (AIT) in the magnetic equatorial region by high frequency (HF) electromagnetic (EM) waves injected into the overhead ionospheric layer is examined. EM waves with ordinary (O) mode polarization reach the critical layer only if their incidence angle is within the Spitze cone. Near the critical layer the wave electric field is linearly polarized and directed parallel to the magnetic field lines. For large enough amplitudes, the O mode becomes unstable to the 4-wave oscillating two-stream instability (OTSI) and the 3-wave parametric decay instability (PDI) driving large amplitude Langmuir and ion acoustic waves. The interaction between the induced Langmuir turbulence and electrons located within the 50-100 km wide transmitter heating cone at an altitude of 230 km can potentially accelerate the electrons along the magnetic field to several tens to a few hundreds of eV, far beyond the thresholds for optical emissions and ionization of the neutral gas. It could furthermore result in generation of shear Alfvén waves such as have been recently observed in laboratory experiments at the UCLA Large Plasma Device (LAPD).