Dropouts of the outer electron radiation belt in response to solar wind stream interfaces: global positioning system observations
Dropouts of the outer electron radiation belt in response to solar wind stream interfaces: global positioning system observations
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DOI：
10.1098/rspa.2010.0078
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发表时间：
2010-11
期刊：
影响因子：
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通讯作者：
S. Morley;R. Friedel;E. Spanswick;G. Reeves;J. Steinberg;J. Koller;T. Cayton;E. Noveroske
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文献类型：
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作者：
S. Morley;R. Friedel;E. Spanswick;G. Reeves;J. Steinberg;J. Koller;T. Cayton;E. Noveroske
我们结合全球定位系统(GPS)星座上9台组合X射线剂量计的数据，对一系列漂移壳(L和GT；4)上的电子辐射带中的相对论电子计数进行了统计研究。对67个太阳风流界面(SIS)的电子数随时间、能量和漂移壳层的响应进行了统计检验，并用CXD资料进行了二维叠加历元分析。对于这些时期，我们研究了辐射带的丢失和关键地球物理参数的同步变化。在较高的L，我们观察到了SI前一天电子计数逐渐下降的趋势，这与向外扩散和磁层顶阴影是一致的。L*，辍学发生的中位数时间尺度为≃7小时，中位数下降0.41.8个数量级。辐射带脱落和恢复的中心趋势既取决于L*，也取决于能量。对于≃，70%的纪元Sym-H超过−30nT，但67个SI中只有3个在电子数据中没有相关的辍学。电子沉淀统计图表明，在高速流驱动下，合唱驱动的相对论电子微爆发可能是辐射带损失的主要贡献者。
We present a statistical study of relativistic electron counts in the electron radiation belt across a range of drift shells (L*>4) combining data from nine combined X-ray dosimeters (CXD) on the global positioning system (GPS) constellation. The response of the electron counts as functions of time, energy and drift shell are examined statistically for 67 solar wind stream interfaces (SIs); two-dimensional superposed epoch analysis is performed with the CXD data. For these epochs we study the radiation belt dropouts and concurrent variations in key geophysical parameters. At higher L* we observe a tendency for a gradual drop in the electron counts over the day preceding the SI, consistent with outward diffusion and magnetopause shadowing. At all L*, dropouts occur with a median time scale of ≃7 h and median counts fall by 0.4–1.8 orders of magnitude. The central tendencies of radiation belt dropout and recovery depend on both L* and energy. For ≃70 per cent of epochs Sym-H more than −30 nT, yet only three of 67 SIs did not have an associated dropout in the electron data. Statistical maps of electron precipitation suggest that chorus-driven relativistic electron microbursts might be major contributors to radiation belt losses under high-speed stream driving.