Theoretical And Experimental Study On The Incoherent Scatter Spectra Of High Latitude Auroral Ionosphere

Based on the theoretical study of Non-Maxwellian ionosphere plasma, the Non-Maxwellian ion distribution function, the Non-Maxwellian incoherent scatter spectra and the interpretations from the theories and experiments on the origin of Naturally Enhanced Ion Acoustic Lines (NEIAL) in the high latitude auroral ionosphere are investigated in this dissertation. A thorough relevant research reveals that the study on the Non-Maxwellian ion distribution and the Non-Maxwellian incoherent scatter spectra is just a preliminary work, and the interpretation on the origin of NEIAL also remains controversial. Consequently, this dissertation focuses on the work of the Non-Maxwellian ion distribution, the Non-Maxwellian incoherent scatter spectra and the interpretation on the origin of NEIAL. With the development of the incoherent scatter radar and the ionospheric heating, this field has become one of the hot topics in ionospheric study using the incoherent scatter radar, and is in urgent need for further study. As a basis of this dissertation, a brief review is firstly presented on the characteristics of the ionosphere plasma. The main works are as follows.Firstly, based on the incoherent scatter theories of ionosphere plasma, using the formulas of the incoherent scatter spectra of the collision and non-collision plasma without considering the magnetic field, the Maxwellian ion distribution function and the incoherent scatter spectra are calculated and discussed.Secondly, according to the Boltzmann's equations, the Boltzmann collision integral is represented with a simple relaxation collision model and the Maxwell molecule collision model, respectively. The ion velocity distribution function is described by 5-moment approximation, 13-moment approximation and 20-moment approximation based on Maxwellian distribution or by 6-moment approximation, 16-moment approxi- mation based on bi-Maxwellian distribution, respectively. The ion temperature, the ion drift velocity, the ion temperature, the stress tensor and the heat flow vector are obtained from the transport equations of the relaxation collision model and the Maxwell molecule collision model, respectively. The expressions of the ion velocity distributions of 5-moment approximation, 13-moment approximation, 20-moment approximation, 6-moment approximation and 16-moment approximation are derived. The comparison of the solutions of the transport equations and the ion velocity distribution between the relaxation collision model and the Maxwell molecule collision model are discussed. Thirdly, using the ion velocity distribution of the relaxation collision model and the Maxwell molecule collision model, the incoherent scatter spectra are calculated with the Sheffield's incoherent scatter theories. The comparisons of the incoherent scatter spectra obtained by above two collision models are discussed.Fourthly, considering the phenomenon of NEIAL, which have been frequently observed by incoherent scatter radar in the high latitude auroral ionosphere, three different theories available are discussed to interpret the origin of NEIAL in the auroral ionosphere. By introducing the field-aligned heat flow, the current driven ion acoustic instability and the ion-ion two stream instability are modified, which can interpret NEIAL better.Finally, combining the EISCAT radar data and the others related method of the observation, such as optical detection (Meridian scanning photometer, All Sky TV Camera), the two NEIAL events are selected and discussed, and reason for the NEIAL occurring is obtained. According to theories of the field-aligned current instability and the modified field-aligned current instability, the reasonable ionosphere plasma parameters are inversed and obtained from the incoherent scatter radar data.