Development and preliminary observational result of Low-Frequency Magnetic Field Wave Receivers for Phase II of Meridian Project

The geomagnetic field is an important factor in space environment monitoring. Under disturbed conditions, it exhibits ultra-low-frequency geomagnetic pulsations characterized by broad frequency ranges, large amplitude, and long duration. In addition, very-low-frequency electromagnetic waves are also prevalent in geospace. These waves are important physical processes in space physics and space weather study, and are one of the main targets of the Meridian Project. To comprehensively monitor these waves in geospace, Phase II of the Meridian Project has deployed four sets of Low-Frequency Magnetic Field Wave Receivers along the 40°N latitude (Jilin Nong'an Station, Inner Mongolia Siziwang Station, Gansu Yuzhong Station and Xinjiang Hutubi Station), enabling continuous 24-hour monitoring of waves at low frequency bands (Very Low-Frequency waves and Ultra-Low-Frequency waves). This paper presents the technical specifications, testing and preliminary observational results of the Low-Frequency Magnetic Field Wave Receivers. The preliminary observations show that on May 10, 2024, the Low-Frequency Magnetic Field Wave Receivers at all four stations detected the same geomagnetic pulsation event, which was also recorded by the Broadband Geomagnetic Wave Monitoring Instrument at the Meridian Project’s Ledong Station in Hainan. Furthermore, on August 30, 2025, the Low-Frequency Magnetic Field Wave Receiver at the Hutubi Station in Xinjiang detected an electromagnetic disturbance in the very-low-frequency range. These results demonstrate that the four Low-Frequency Magnetic Field Wave Receivers deployed in Phase II of the Meridian Project are capable of effectively observing electromagnetic wave fluctuations.