Study On The Incoherent Scatter Spectra And Its Application In The Ionospheric Heating

On the basis of theoretical study on the incoherent scatter, the effects of the non-equilibrium plasma induced by ionospheric heating on power spectra have been studied in this dissertation. The current incoherent scatter data analysis is based on the standard Maxwellian distribution, however, non-Maxwellian distribution characteristics of the ionospheric plasma can be induced by high power radio wave. Consequently, this dissertation is focused on the study on the incoherent scatter spectra with the non-Maxwellian distribution. As basis, a brief introduction is given on the incoherent scatter theory, measurement and data analysis firstly. The main topics and results are as follows:First, the relationship between the ionosphere parameters and spectra characteristic is discussed with the Maxwellian distribution and the incoherent scatter spectra of the high-order distribution in convection electric field are calculated. Taking in the consideration of the elastic collision between electrons and neural particles and the excitation of the rotation energy level, the electron velocity distribution function and the incoherent scatter spectra during ionospheric heating in low ionosphere region are presented. With the decrease of electric field, the amplitude of spectra is enhanced and the width of spectra becomes narrow. With the increase of pump frequency, the power spectra tend to be the Maxwellian case. According to the analysis above, it is suggested that the effect of high frequency (HF) heating can be enhanced by the increase of the transmitter power and decrease of the pump frequency.Second, the velocity distribution function can be achieved by solving the Boltzmann's equation in the approximation condition, however, only the empirical model can be used to describe the non-Maxwellian characteristic of the distribution function in general. The non-Maxwellian high-tail of the electron distribution function induced by HF heating can be modeled by the super-Gaussian and Lorenzian distribution, and the effect of the non-Maxwellian index on the ion and plasma line are discussed. The empirical models with the energetic electrons and artifical field-aligned irregularity (AFAI) are also presented, and the effects of the concentration and velocity of the energetic electrons and the irregularity temperature on the incoherent scatter spectra are discussed.Third, the incoherent scatter spectra of a collisional plasma with an arbitrary velocity distribution function is presented. Two integrals with complex singular points have been solved in order to obtain the results. In the artificial modification space environment, the useful electron distribution functions to model such plasma are the generalized super-Gaussian and Lorenzian distribution. The effects of collisional frequency on spectra are discussed. With the different collisional frequency, the control mechanisms of the non-Maxwellian factor and ionospheric parameters are compared. Under the action of collision frequency, the original relationship between ionospheric parameters and the characteristics of spectra shape is invalid, which will bring a large error in the inversion of ionosphere parameters. On account of the obvious effect of the collision on spectra shape, the collision frequency can be use as an independent parameter in the incoherent scatter data analysis.Fourth, according to the analysis of the observation data, the heating effects in polar winter ionospheric modification experiments carried out in January 2008 at Troms?, Norway were studied. A clear disturbance effect is present under the O-mode over-dense heating conditions. The enhancement of the electron temperature is up to 60%~120%, extending from 150 km to 400 km;The disturbance of the electron density is not obvious, with a 12% maximum decrease. An increase of 1~2 kHz in the acoustic frequency can be observed; an enhancement in the peak-to-valley ratio of the ion line and sometimes its high-order harmonics can be seen as well. The power of the ion line and plasma line has shown overshoot effect, single-humped, double-humped and triple-humped structures have appeared in the power profile of plasma line, and the enhancement in power amplitude of the plasma line decreases exponentially as the frequency increases.Fifth, according to the incoherent scatter model of the artificial field-aligned irregularities and the collision plasma with non-Maxwellian distribution in the low ionosphere heating, the measured data in polar winter ionospheric modification experiments carried out in January 2008 at Troms? are analyzed. Compare to the AFAI model, the electron temperature is underestimated and the electron density is overestimated by the Maxwellian model. The electron fluxes from the AFAI model, which can excite 630.0nm and 557.7nm airglow, are much larger than that from the Maxwellian model. It is means that the AFAI model can give a better explanation of the radio-induced aurora. Using super-Gaussian model, the obvious electron temperature enhancement can be seen in this experiment, and there is a correlation between the temperature and the polarized state, the enhancement with X model heating is more obvious. The heating electric field is also deduced from the non-Maxwellian index. It is means that the electric field becomes an independent inversion parameter instead of an estimated value from theoretical model.Finally, the 1D and 2D numerical simulation model of the ionospheric heating is presented, and the heating effects of the electron density and temperature, the absorption and loss rates of the wave energy, the recombination coefficient and the thermal conductivity coefficient in polar ionosphere are discussed. The effects of the pump parameters are argued, and the heating characteristic increases with the increment of the heating power and the decrement of the pump frequency. The amplitude of the ionospheric parameters are controlled by both power and frequency, however, the frequency can also affect the position and shape of the parameters. The simulation results of the 1D and 2D model are compared, and the results are compared with the measured data. In the light of neglecting the transverse factors, an overestimation of the electron temperature increment and an underestimation of the density attenuation are induced by 1D simulation.