预加热时间对低电离层预加热幅度调制的影响

基于电离层连续方程和能量方程，建立预加热模式下低电离层幅度调制加热理论模型，模拟大功率电波幅度调制电离层电导率和电流随时间的变化，分析预加热时间对幅度调制产生的极低频/甚低频（ELF/VLF）强度的影响.结果表明，低电离层中的电流能够被大功率电波有效调制，可以作为ELF/VLF电波的辐射源.预加热幅度调制模式在预加热时间较长时效果更明显.在考虑能耗的情况下，当有效辐射功率为200MW及高频波的调制频率f_ELF/VLF为1kHz时，预加热幅度调制模式辐射ELF/VLF加热0.1s时效果最好，强度可提高约7.95dB. 

Effects of Pre-heating Time on Pre-heating Amplitude-modulation in the Lower Ionosphere

Based on the energy conservation equation and electron continuity equation, the pre-heating amplitude-modulated theoretical model for the lower ionosphere is established. Then, the oscillations process of ionospheric conductivity and current, which amplitude are modulated by high power electric wave are simulated. Furthermore, the effects of pre-heating time on Extremely Low Frequency/Very Low Frequency (ELF/VLF) radiation levels are studied thoroughly. The results indicate that the electric current in the lower ionosphere can be modulated effectively by high power electric wave, and can be used as the radiation source of ELF/VLF. The longer the pre-heating time is, the more effectively the pre-heating amplitude-modulated model is. If taking the energy loss into account, as the heating conditions are P_ER=200MW and f_ELF/VLF=1kHz, the effect of ELF/VLF radiation with the pre-heating amplitude-modulated model is the best when the pre-heating time is 0.1s. And the ELF/VLF radiation levels are improved by 7.95dB.