Short-term variations of the inner radiation belt in the South Atlantic anomaly
Short-term variations of the inner radiation belt in the South Atlantic anomaly
复制标题
南大西洋内辐射带异常的短期变化
DOI：
10.1002/2015ja021312
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发表时间：
2015
影响因子：
2.8
通讯作者：
Zhang Xianguo
中科院分区：
文献类型：
--
作者：
Zou Hong;Li Chenfang;Zong Qiugang;Parks George K.;Pu Zuyin;Chen Hongfei;Xie Lun;Zhang Xianguo
南大西洋异常（SAA）的长期变化通常是通过拟合高斯函数来获得的，该函数是在一定高度上累积一个月或更长时间的质子通量的平均分布。这些数据并没有显示出由时间尺度小于一个月的磁暴效应引起的SAA的短期变化。为了研究太阳辐射的短期变化，采用5天移动平均法，对1998-2008年期间NOAA极轨环境卫星探测到的高能质子的太阳辐射特征进行了研究。结果表明，磁暴期间，三个质子通道的两个SAA参数反映了SAA中最大的质子通量，SAA的扩展减小了几个百分点。讨论了高能质子两个SAA参数减小的可能原因。内辐射带外边界的质子损失可用磁力线曲率散射机制解释，而SAA中心附近质子通量的减少可能是磁暴期间中性大气密度增强所致。对SAA中高能质子行为的研究有助于理解风暴时间和地球附近辐射环境的长期变化，并有助于构建动态辐射带模型。
Long‐term variations of South Atlantic anomaly (SAA) are generally derived by fitting a Gaussian‐like function to an averaged distribution of the proton flux at a certain altitude accumulated over time periods for a month or longer. These data do not show the short‐term variation of SAA arising from geomagnetic storm effects whose time scale is less than a month. To investigate the short‐term variations, the features of SAA for the high‐energy protons detected by NOAA Polar Orbiting Environmental Satellites during 1998–2008 have been investigated with a 5 day running average method. It is found that the two SAA parameters for three proton channels reflect the maximal proton flux in SAA and the extension of SAA decreases several percent during geomagnetic storms. Possible reasons for the decreases of the two SAA parameters for high‐energy protons are discussed. Proton losses at the outer boundary of the inner radiation belt can be explained by the field line curvature scattering mechanism, while the decrease of the proton flux near the center of SAA is probably caused by the enhanced neutral atmospheric density during geomagnetic storms. The study of the behavior of high‐energy protons in SAA is useful for understanding of storm time and long‐term variations of the radiation environment near Earth and for constructing dynamic radiation belt models.