The Characteristics of Ionosphere Modulation by Magnetosphere Ultra-low Frequency Waves During 2024 Mother Day Geomagnetic Storms

Using ground-based magnetometer data and GNSS data from the Chinese Meridian Project, we investigate ULF wave within Pc4 frequency bands modulating total electron content (TEC) of ionosphere in the midlatitude region, during the period of 2024 Mother Day Geomagnetic Storms. The amplitude of PC4 wave can reach 56.5nT, which is the largest amplitude of PC4 in the midlatitude region. This geomagnetic field disturbance account for 0.025% of background geomagnetic field, while it can trigger a ten-times, i.e., 0.25% TEC variation. The amplitude of TEC variation can reach to 0.4 TECU, which is 3 times of the TEC variation in quiet day. This modulation process covers a wide space region with 40 longitude span of 40 degrees and latitude span of 20 degrees. These results provide us new knowledge about the coupling between the solar wind-magnetosphere-ionosphere in midlatitude regions, and have the potential significance on evaluating the effect of space weather of this coupling process.