Case study of radio emission beam associated to very low frequency signal recorded onboard CSES satellite

We report on the variation of electric power density linked to very low frequency (VLF) signal observed during the minimum of solar cycle 25. The detected VLF signal is emitted by the NWC radio station localized in the southern hemisphere, at 21.5?degrees S and 114.2 degrees E. We attempt in this work to quantify the beam as detected by the Electric Field Detector (EFD) instrument onboard CSES satellite. Geometrical key parameters have been considered to analysis the variation of the power density taking into consideration the distance between the satellite trajectory and the NWC station and its conjugate region. The beam behavior is found to be subject to significant disturbances in the conjugate region with the presence of signal modulations. Above the NWC transmitter station, the beam can be considered as a hollow cone but with irregularity dependence on the electric power density.