Analysis of ground-based very low frequency signal recorded onboard CSES satellite

Abstract : We report on the wave spectral intensity variations associated to very low frequency (VLF) signal observed during the minimum of solar cycle 25. The VLF signal is emitted by the ground-based NWC radio station localized in the southern hemisphere, at −21.5°S and 114°E. The variation of NWC radio signals is daily detected by the electric field experiment EFD onboard the China Seismo-Electromagnetic Satellite (CSES). This satellite has an altitude of about 507 km in a polar and circular sun-synchronous orbit with local time nodes of 02 LT and 14 LT. We study the spectral intensity variations at the frequency of 19.79 kHz in three specific regions: above the NWC station, around the magnetic equatorial plane, and at the conjugate point. We analyze the electric flux above those key regions and estimate the corresponding intensity levels.