中文摘要：

基于电离层连续性方程和能量方程,建立了预加热模式下低电离层幅度调制加热理论模型,研究预加热阶段电离层电子密度和调制阶段电流随预加热时间的变化,探讨不同背景条件对幅度调制产生的极低频/甚低频（ELF/VLF）电磁波强度的影响.结果表明,预加热调制在90～100 km高度效果较好,在夜间进行预加热调制激发的ELF/VLF强度增幅不明显,各季节中在春季调制强度增幅最大,太阳高年预加热调制比太阳低年的效果好,低纬地区强度增幅远大于中纬地区强度增幅.在一定加热条件下（有效辐射功率200 MW,频率1 kHz）,不同背景条件（除夜间外）下的预加热幅度调制模式在考虑能耗情况下,均在预加热10 s时效果最好.

英文摘要：

Based on the energy conservation equation and electron continuity equation, the Pre- heating Amplitude-Modulated Theoretical Model （PAMTM） of ionospheric current modulated by powerful HF radio waves, is constructed. The oscillations process of ionospheric density in pre- heating period and current in modulation period are analyzed. Moreover, the effects of different background condition on radiation strength of electromagnetic wave in Extremely Low Frequen- cy/Very Low Frequency （ELF/VLF） band are studied in details by use of PAMTM. The results indicate that PAMTM is more effective in the daytime than in the nighttime. It has the largest strength increment in spring and the intensity of pre-heating amplitude at solar maximum is bigger than that of solar minimum. Its intensity increment amplitude at low latitude is stronger than that of middle latitude. Under certain heating conditions （fERP = 200 MW, fELF/VLF = 1 kHz）, the effect of the PAMTM is the best when the pre-heating time is 10 s considering energy loss, and ELF/VLF radiation levels can be improved by 10.00 dB.