Investigation on Matching Conditions of Langmuir Parametric Instability in Ionospheric Heating

Parametric decay instability (PDI) is an important process in ionospheric heating. HFPLs and HFILs in spectra of ISR are the direct observational evidences of PDI excitation. Stimulated electromagnetic emissions (SEE), enhanced airglow and artificial ionized layer are also closely related to PDI. The focus of this talk will be on the generation of PDI and Langmuir turbulence based recent observational and simulational study. This presentation includes a few topics: (1) Recent heating experiments presented excitation of PDI during the O-mode heating period by EISCAT. We suggest that the full dispersion relationship of the Langmuir wave can be employed to analyze the O-mode parametric instability excitation. A modified kinetic electron distribution is proposed to satisfy the matching condition of parametric instability excitation. (2) The simulation results of 1D Zakharov model show that caviton collapse dominate in higher altitude area and cascade dominate in lower altitude, which is consistent with strong Langmuir theory (SLT). Based on the spectrum analysis, the development of PDI to Langmuir turbulence is investigated in details. (3) Langmuir turbulence leads to strong electron acceleration. Generation mechanism of Langmuir turbulence and electron acceleration are also discussed with the help of numerical simulations.