摘要
The central position of the South Atlantic Anomaly(SAA)has been drifting westward or northward,and the drift speeds exhibit a complex relationship with solar activity,which also affects the area of the SAA configuration.Using six years of data from the low-Earth orbit satellite CSES,we analyze the spatiotemporal evolution of the geomagnetic field and high-energy protons within the SAA during Solar Cycle 25.Low-energy protons(2.0-10.0 MeV)exhibit a characteristic double-peak structure,whereas high-energy protons(10.0-20.0 Me V)display a single-peak profile—consistent with observations from NOAA/MEPED.By fitting a Double-Gaussian distribution in both latitude and longitude from January 2019 to April 2024,we find that the center of the SAA proton distribution drifted northward at an average speed of 0.29±0.12°/yr(dayside).At the same time,the SAA proton center drifted westward at speeds of 0.36±0.08°/yr(dayside)and 0.33±0.10°/yr(nightside).Notably,lower-energy protons drift slightly faster.The geomagnetic field variations in the SAA region observed by CSES are generally consistent with the IGRF-13 model.Based on IGRF-13,we calculate drift speeds from 2015 to 2025 to be 0.014±0.002°/yr in the northward(latitudinal)direction and 0.282±0.030°/yr in the westward(longitudinal)direction.Quantitative boundary analysis further indicates that the area of the SAA decreased by 6.09%±1.03%from 2019 to 2024,showing a negative correlation with solar activity.These findings contribute to the understanding of SAA dynamics and the near-Earth radiation and electromagnetic environment during this current solar activity cycle.
基金
supported by the National Natural Science Foundation of China(Grant Nos.42474222,12173038&41904149)
the National Key Research and Development Program Project(Grant No.2023YFE0117300)。
