Investigation of VLF Transmitter Signals in the Ionosphere by ZH‐1 Observations and Full‐Wave Simulation

Abstract In this study, we investigate the very low frequency (VLF) signals in the ionosphere propagating from ground‐based transmitters by using the data from the newly launched China Seismo‐Electromagnetic Satellite (CSES), which is also called ZH‐1. The simultaneous ionospheric perturbations and electron precipitations induced by the NWC transmitter are also analyzed, and the possible mechanisms are discussed. The ZH‐1 and DEMETER observations of VLF transmitters are compared morphologically, which are generally consistent with the full‐wave simulations. The results show that the electromagnetic waves excited by the VLF transmitters penetrate into the ionosphere and propagate in the magnetosphere to its conjugate hemisphere as a ducted or nonducted whistler. When the VLF transmitter is located at L < 1.5, the wave propagates more easily as a nonducted whistler. When the wave propagates as a ducted whistler, the point of maximum observed transmitter‐induced electric field in the conjugate hemisphere will move poleward in the northern hemisphere and equatorward in the southern hemisphere. The results also show that the data stability of electromagnetic field recorded by ZH‐1 satellite is almost the same as DEMETER satellite, and there is a good correlation between the ZH‐1 observation and simulated results. These conclusions demonstrate that the nightside VLF band electromagnetic observation of ZH‐1 satellite is stable and reliable.