低高度内辐射带高能质子空间分布位形的研究

THE STUDY OF SPACE DISTRIBUTIONCONFIGURATION OF THE RADBELT PROTONSWITH HIGH ENERGY

利用国际地磁参考场模式(IGRF模式)分析了1970—2000年低高度南大西洋负磁异常区位形的漂移与变化,给出了几个高度异常区中心位置磁场强度的变化和位置的变化。利用带电粒子的运动学方程,简要分析了低高度辐射带高能粒子的运动,得出在低高度,磁场是决定辐射带高能粒子空间强度与分布的决定性因素。低高度辐射带空间分布位形的变化特征应该与低高度南大西洋负磁异常区的变化特征基本一致。低高度南大西洋负磁异常区的特征可以作为低高度辐射带空间分布位形的一个初步判据。

By using International Geomagnetic Reference Field (IGRF), the paper computes the drift of South Atlantic Anomaly (SAA) region at several altitudes lower than 1 000 km for the interval of 1970-2000. The results show that the center of the SAA moves 4-6 towards west, while the center of the SAA no more than 1?towards the north. The extent of the SAA in the year 2000 includes that of the SAA in 1970 and its coverage extends with some scale in both latitude and longitude directions. The value of geomagnetic field strength at the center of SAA in 2000 is lower than that in 1970. The biggest scale for the decrease in geomagnetic field strength at the center of the SAA is no more than 3.87% for the altitudes lower than 1000 km. It is enough to use internal field for the altitudes lower than 1000 km, so the results are reliable. The charged particles with energy higher than 10 MeV mainly distribute in the SAA region for low altitudes based on AP8 Model, but the model was just suit for epoch 1960 to 1970. Because the kinetic properties of a charged particle are almost completely decided by the properties of the geomagnetic field at altitudes lower than 1000 km, so we can know the charged particles with energy higher than 10 MeV still distribute in SAA region. The space distribution configuration of charged particles with high energy should basically be consistent with the space distribution configuration of the geomagnetic field for low altitudes. The space configuration of the SAA region in low altitudes can be considered as the criterion of the space configuration of radiation belt protons with energy higher than 10 MeV.