考虑电子吸附效应的低电离层加热研究

摘要

基于低电离层自洽加热模型,综合考虑了低电离层中电子的复合效应及典型吸附效应,本文数值仿真了大功率高频无线电波持续加热低电离层所产生的电子温度、电子密度的扰动,并且首次模拟分析了由于电子温度扰动造成的加热电波自吸收效应.结果表明:电子吸收大功率加热电波能量导致了电子温度的增加,同时改变了电离层的吸收指数,引起了加热电波的自吸收效应.加热电波的自吸收效应对低电离层较高区域的电子温度扰动有重要的抑制作用.因此,随着加热频率的减小或有效辐射功率的增大,低电离层较低区域的电子温度增量明显增大而在高度100 km以上区域的电子温度增量始终较小.另一方面,随着电子温度的增加,电子的复合系数减小而电子的吸附系数增加,导致了电子密度在低电离层中较高区域出现正扰动而在较低区域出现负扰动.当饱和电子温度较大时,继续减小加热频率或增大有效辐射功率对电子密度扰动所造成的改变较小,尤其当电子温度超出复合系数和吸附系数的温度敏感区间.此外,电子温度与电子密度的饱和时间相差较大,电子温度的饱和时间为微秒量级而电子密度的饱和时间为秒量级.%Based on the self-consistent heating model of the lower ionosphere,this paper considers the recombination and attachment effects of electrons in the lower ionosphere.Disturbances of electron temperature and density are simulated during high-power continuous wave incident in the lower ionosphere at middle latitudes.Resulting from disturbance in electron temperature,the self-absorption effect of heating waves is simulated and analyzed for the first time.Results show that electrons absorb energy from a powerful heating wave,leading to increase of electron temperature.The self-absorption poses significant restraining effect on electron temperature disturbance at high latitudes.Therefore,electron temperature increments above 100 km altitude remain constantly small but significantly increase at lower latitudes when the heating frequency decreases or the effective radiated power increases.On the other hand,the recombination rate decreases and the attachment rate increases with growth of electron temperature.Thus,the electron density decreases at low altitudes and then increases at high altitudes.Continuously decreasing the heating frequency or increasing the effective radiation power can lead to minimal influence changing electron density disturbance when the heating electron temperature is high,especially when the heating electron temperature exceeds the sensitive region about electron recombination coefficients and electron attachment coefficients.In the lower ionosphere,a large gap exists between the characteristic saturation times of electron temperature and electron density;the former is in the order of microseconds,whereas the latter is in the order of seconds.