大功率高频电波加热电离层中参量衰减不稳定性研究(2):EISCAT实验观测

Study of parametric decay instability in powerful wave ionospheric heating(2):Experimental observations from EISCAT

本文利用欧洲非相干散射雷达协会(European Incoherent Scatter Scientific Association,EISCAT)的两次加热实验诊断数据,基于我们在文章(1)中建立的数值模型,定量分析了实验过程中出现参量衰减不稳定性(Parametric decay instability,PDI)的物理过程.分析结果如下:(1)通过对两次加热实验数据的分析,均观测到了增强的等离子体谱线(HFPLs)和离子声波谱线(HFILs),谱线的频率和加热电波频率满足频率匹配条件,表明电离层加热过程中参量衰减不稳定性的激发.(2)通过对加热电波反射区电子密度和离子密度模拟数据的谱分析,可以清晰发现与实验结果相符的朗缪尔波和离子声波.实验1观测到的离子声波谱线频率为8.8 kHz,而模拟得到的离子声波在5～6 kHz,实验2观测到的离子声波谱线为7.1 kHz,而模拟得到的离子声波频率在5.5～6 kHz,模拟结果与实验观测比较一致.(3)实验观测和模拟结果均表明,在参量衰减不稳定性激发过程中,加热电波频率(f_h)与等离子谱线频率和离子声波谱线频率(f_(ia))并不是简单匹配,实验1观测到的等离子体谱线频率为f_h-3f_(ia),实验2观测到的等离子体谱线增强频率为f_h—f_(ia)和f_h—3f_(ia).这一结果表明在加热过程中出现了多次参量衰减的现象,从而为朗缪尔湍流的激发提供了条件.

Based on the ionospheric heating experiment of EISCAT in 2012.10.19 LT, the PDI （Parametric decay instability） in the experiment is analyzed.Numerical simulation is conducted, which is compared with experiment.The results could be summarized as follows： （1）The enhancement of plasma line and ion line is observed, while the Langmiur wave and ion acoustic wave occur in the simulation. （2） The frequency of ion line enhancement observed in case 1 is about 8.8 kHz, which in case 2 is 7.1 kHz, and the frequency of ion acoustic wave from the simulation is about 5~6 kHz in case 1 and 5.5~6 kHz in case 2. （3） The results of case 1 and case 2 demonstrate that heating wave frequency （fh） does not match the plasma lines and ion acoustic lines （fia）.Electron plasma line frequency observed is about fh-3fia in case 1 and fh-fia,fh-3fia in case 2.Simulation results demonstrate that farther decay occurs.