The PI will perform theoretical investigations of HF-induced plasma turbulence in the ionosphere, dealing with: (1) improving fundamental physical descriptions included in simulation codes for treating HF induced Langmuir turbulence, and (2) applying the Langmuir turbulence theory to the prediction of hot electrons and airglow, the excitation of Langmuir turbulence by beat wave excitation, simultaneously employing two heater frequencies differing by a local ionospheric plasma frequency, the simulation of probe signatures on a wounding rocket traversing the HF induced turbulent region, analysis of the excitation of the two-plasmon decay instability and stimulated Raman scattering in the ionosphere, and mesoscale phenomena involving the self-consistent propagation of heater wave in its induced turbulence and modified density profile.