低电离层调制激励VLF/ELF辐射参数优化理论分析

Theoretical analysis of parameter optimization for lower-ionosphere modulated excitation VLF/ELF waves

针对低电离层幅度调制加热过程中甚低频/极低频(VLF/ELF)激发效率较低的问题,该文利用低电离层调制加热模型分析方波幅度调制加热过程中占空比和加热频率对VLF/ELF辐射效率的影响,在此基础上获得最大VLF/ELF辐射效率下的优化占空比和加热频率选择范围.研究表明,随着调制波占空比的增大,激发的VLF/ELF等效辐射源强度先增大后减小,占空比的优化范围为40%~70%;随着加热频率的增大,激发的VLF/ELF等效辐射源强度先增大后减小,加热频率的优化范围为(0.8~0.9)倍低电离层临界频率.

In order to improve the radiation efficiency of VLF/ELF in amplitude modulated ionospheric heating experiments, taking the square wave AM heating for example, the duty cycle and heating frequency, which have an significant effect on VLF/ELF radiation efficiency, are analyzed and discussed by using the lower-ionosphere modulated heating model. Based on the numerical simulation, the ranges of parameter selection of optimal duty cycle and the heating frequency are derived. The result shows that the intensity of the VLF/ELF equivalent radiation source firstly increases and then decreases with increase of the modulated duty cycle and heating frequency. The optimal duty cycle varies between 40% and 70%, and the optimized heating frequency is 0.8-0.9 times the critical frequency of the lower-ionosphere.