Experimental Investigation of the Dynamic Effects of Time-Varying Plasma on Low-Frequency Electromagnetic Wave Propagation

In this paper, we reveal the dynamic effects of time-varying plasma on low-frequency (LF) electromagnetic (EM) wave propagation. The time-varying attenuation, time-varying phase shift, and power spectrum of the LF EM waves are presented. By using the frequency division multiplexing method, LF EM waves at the four discrete frequencies simultaneously penetrate through a shared time-varying plasma in one shock tube experiment. The experimental results indicate that the time-varying attenuation and phase shift of the LF EM wave are determined by the time-varying behavior of the plasma, and they are positively related to the electron density and frequency of the LF EM waves. The theoretical results are well consistent with the experimental results. Moreover, in the frequency domain, the time-varying plasma causes spectrum expansion of the LF EM waves. These results help us deeply understand the propagation process of LF EM waves in time-varying plasma and design LF communication systems.