Geosynchronous Orbit辐射带对快速反向冲击的响应
Radiation Belt Response to Fast Reverse Shock at Geosynchronous Orbit
摘要：
快速反向冲击（FRSs）导致磁层膨胀，这与众所周知的由快速正向冲击（FFS）造成的压缩相反。通常，FFS比FRS更具地球效应，因此，对两种冲击类型的内磁层动态响应可能会有很大不同。在这项研究中，我们调查的第一次使用多卫星观测和数值模拟的FRS影响的辐射带的响应。向阳面的航天器观测到磁场强度和高能（~ 40-475 keV）粒子通量的下降。时序分析表明，磁场信号是从昼侧磁层向夜侧磁层传播的。具有不同能量的粒子在每个航天器上同时变化，这意味着对冲击的非分散粒子响应。位于较低L壳层的航天器没有记录到任何显著的信号。观测结果表明，与冲击倾斜度相关的响应依赖于当地时间，在黄昏-午夜部门观察到最清晰的签名。模拟低估了在夜面观测到的磁场变化幅度。所观察到的电子强度的降低是径向梯度和绝热效应共同作用的结果。在光谱指数的径向梯度似乎是占主导地位的贡献者所观察到的变化的电子在白天（近中午和黄昏）和在黑夜（近午夜）。这项研究表明，即使是一个FRS可以影响辐射带显着，并提供了一个机会，以了解他们的动态响应磁层的突然膨胀。
英文摘要：
Fast reverse shocks (FRSs) cause the magnetosphere to expand, by contrast to the well-known compressions caused by the impact of fast forward shocks (FFS). Usually, FFSs are more geoeffective than FRSs, and consequently, the inner magnetosphere dynamic responses to both shock types can be quite different. In this study, we investigate for the first time the radiation belt response to an FRS impact using multi-satellite observations and numerical simulations. Spacecraft on the dayside observed decreases in magnetic field strength and energetic (~ 40-475 keV) particle fluxes. Timing analysis shows that the magnetic field signature propagated from the dayside to the nightside magnetosphere. Particles with different energies vary simultaneously at each spacecraft, implying a non-dispersive particle response to the shock. Spacecraft located at lower L-shells did not record any significant signatures. The observations indicate a local time dependence of the response associated with the shock inclination, with the clearest signatures being observed in the dusk-midnight sector. Simulations underestimate the amplitude of the magnetic field variations observed on the nightside. The observed decreases in the electron intensities result from a combination of radial gradient and adiabatic effects. The radial gradients in the spectral index appear to be the dominant contributor to the observed variations of electrons seen on the dayside (near noon and dusk) and on the nightside (near midnight). This study shows that even an FRS can affect the radiation belts significantly and provides an opportunity to understand their dynamic response to a sudden expansion of the magnetosphere.
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