On 31 January 2016, the flux of >2 MeV electrons observed by Geostationary Operational Environmental Satellite (GOES)‐13 dropped to the background level during a minor storm main phase (−48 nT). Then, a second storm (−53 nT) occurred on 2 February; during the 3 days after its main phase, the flux remained at background level. Using data from various instruments on the GOES, Polar Operational Environmental Satellites (POES), Radiation Belt Storm Probes (RBSP), Meteor‐M2, and Fengyun‐series spacecraft, we study this long‐term dropout of MeV electrons during two sequential storms of similar magnitude under lightly disturbed solar wind conditions. Observations from low‐altitude satellites show that the fluxes decreased first at higher L‐shells and then gradually propagated inward. Moreover, the fluxes were almost completely lost and dropped to the background level at L > 5, while the fluxes at 4 < L < 5 were partly lost, as observed by RBSP and low‐altitude satellites. Finally, observations show that on 5 February, only the fluxes at L > 5.5 recovered, while the fluxes at 4 < L < 5 did not return to the prestorm levels. These observations indicate that the loss and recovery processes developed first at higher L‐shells. Phase space density (PSD) analysis shows that radial outward diffusion was the main reason for the dropout at higher L‐shells. Regarding electron enhancement, stronger inward diffusion was accompanied by ultra‐low‐frequency (ULF) wave activities at higher L‐shells, and chorus waves observed at outer L‐shells provided conditions for relativistic electron flux recovery to the prestorm levels.

中文翻译：

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两次连续地磁暴期间外辐射带中相对论电子的长期下降

2016年1月31日，对地静止运行环境卫星（GOES）-13观测到的> 2 MeV电子通量在次要风暴主阶段（−48 nT）降至背景水平。然后，2月2日发生了第二场风暴（−53 nT）；在其主要阶段后的三天内，通量保持在背景水平。利用GOES，极地操作环境卫星（POES），辐射带风暴探测器（RBSP），Meteor-M2和风云系列航天器上各种仪器的数据，我们研究了在两次连续暴风雨期间MeV电子的这种长期下降。在轻度扰动的太阳风条件下大小相似。来自低空卫星的观测表明，通量在较高的L壳处首先减小，然后逐渐向内传播。此外，RBSP和低空卫星观测到，在L> 5时，通量几乎完全消失并降至背景水平，而在4 <L <5时，通量部分损失。最后，观测结果表明，在2月5日，只有L> 5.5的通量恢复了，而4 <L <5的通量没有恢复到暴风前的水平。这些观察结果表明，损失和恢复过程首先在较高的L壳层发展。相空间密度（PSD）分析表明，径向向外扩散是高L壳层脱落的主要原因。关于电子增强，较强的向内扩散伴随着在较高L壳处的超低频（ULF）波活动，在外部L壳处观察到的合唱波为相对论电子通量恢复到暴风前水平提供了条件。