FY-3A观测的次南大西洋异常区形成机理

研究FY-3A卫星观测到的内辐射带质子通量分布，发现3～5MeV能道出现除南大西洋异常区以外的第二个异常区.该异常区是一个质子通量的次极值区，由于该质子通量极值区比主南大西洋异常区强度弱、面积小，因此称之为次南大西洋异常区.通过在主南大西洋异常区和次南大西洋异常区分别选取有代表性的样本点进行研究，发现内辐射带质子通量随投掷角近似呈正态分布，当投掷角在90°附近时，质子通量出现极大值；当投掷角大于120°或者小于60°时，质子通量几乎为零.此外，主南大西洋异常区质子通量在各个能道均为完全各向异性，次南大西洋异常区质子通量随着能道增高逐渐趋于各向同性.通过NOAA观测数据对此规律进行了验证，并由此解释了次南大西洋异常区的形成机理. 

Formation Mechanism of Sub South Atlantic Anomaly Region Observed by FY-3A

Based on the proton flux distribution in the inner radiation belt obtained by FY-3A, it is found that the 3~5MeV energy channel shows a second anomalous region besides the South Atlantic Anomaly region. The anomaly zone is a sub-extreme area of proton flux, compared with the main South Atlantic Anomaly region, the new proton flux extremum is weaker and smaller, so it is called the sub South Atlantic Anomaly region. By selecting representative sample points in the main South Atlantic anomaly and sub South Atlantic anomaly areas, the formation mechanism of the sub South Atlantic Anomaly region is studied. The results show that the inner radiation belt proton flux approximately normally distributes with pitch angle, proton fluxes appear at a maximum near the 90° pitch angle; when the pitch angle is greater than 120° or less than 60°, the proton flux is almost zero. In addition, the proton flux in the main South Atlantic Anomaly region is completely anisotropic in each energy channel, and the proton flux in the sub South Atlantic Anomaly region tends to be isotropic as the energy channel increases. And this phenomenon is further verified by the NOAA observation data. Moreover, it is used to explain the formation mechanism of the sub South Atlantic Anomaly region.