The enhancement of cosmic radio noise absorption due to hiss‐driven energetic electron precipitation during substorms
The enhancement of cosmic radio noise absorption due to hiss‐driven energetic electron precipitation during substorms
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DOI：
10.1002/2015ja021113
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发表时间：
2015-07
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通讯作者：
Haimeng Li;Z. Yuan;Xiongdong Yu;Shiyong Huang;Dedong Wang;Zhenzhen Wang;Zheng Qiao;J. Wygant
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文献类型：
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作者：
Haimeng Li;Z. Yuan;Xiongdong Yu;Shiyong Huang;Dedong Wang;Zhenzhen Wang;Zheng Qiao;J. Wygant
利用Van Allen探测器、低空NOAA卫星、MetOp卫星和测力计分析了等离子体层HISS驱动的降水高能电子通量和宇宙射电噪声吸收(CNA)随地磁活动的变化。在地磁平静条件下和亚暴期间，分别观测到了高能电子沉淀(L当地时间4.7-5.3，磁当地时间8-9)。我们发现，在2012年9月6日的安静状态下，由测力计检测到的CNA在嘶嘶声驱动的事件中几乎没有增加。在2012年9月30日的第一次亚风暴期间，由嘶嘶声驱动的里程计增强仍然很小。然而，在2012年9月30日的第二次亚暴期间，测速仪探测到的吸收大大增加，而注入电子的能量变得更高。在第二次亚暴期间，测速仪观测到的CNA(ΔCNA)的增强与用降水高能电子计算的增强是一致的，这意味着在2012年9月30日的第二次亚暴期间，降水高能电子使CNA增加到明显可检测到的水平。这一结论与Rodger等人的结论一致。(2012)，这表明较高水平的ΔCNA更倾向于发生在亚暴中，因为亚暴可能产生与电子注入有关的更强烈的高能电子沉淀。此外，观测和理论计算的结合还表明，高能电子(>；55keV)沉淀比低能电子沉淀对Δ的贡献更大。在本文中，较高能量的电子沉淀与较低频率的嘶嘶声有关。
The Van Allen probes, low‐altitude NOAA satellite, MetOp satellite, and riometer are used to analyze variations of precipitating energetic electron fluxes and cosmic radio noise absorption (CNA) driven by plasmaspheric hiss with respect to geomagnetic activities. The hiss‐driven energetic electron precipitations (at L ~ 4.7–5.3, magnetic local time (MLT) ~ 8–9) are observed during geomagnetic quiet condition and substorms, respectively. We find that the CNA detected by riometers increased very little in the hiss‐driven event during quiet condition on 6 September 2012. The hiss‐driven enhancement of riometer was still little during the first substorm on 30 September 2012. However, the absorption detected by the riometer largely increased, while the energies of the injected electrons became higher during the second substorm on 30 September 2012. The enhancement of CNA (ΔCNA) observed by the riometer and calculated with precipitating energetic electrons is in agreement during the second substorm, implying that the precipitating energetic electrons increase CNA to an obviously detectable level of the riometer during the second substorm on 30 September 2012. The conclusion is consistent with Rodger et al. (2012), which suggest that the higher level of ΔCNA prefers to occur in the substorms, because substorms may produce more intense energetic electron precipitation associated with electron injection. Furthermore, the combination of the observations and theory calculations also suggests that higher‐energy electron (>55 keV) precipitation contributes more to the ΔCNA than the lower energy electron precipitation. In this paper, the higher‐energy electron precipitation is related to lower frequency hiss.