磁云内部与外部注入的太阳高能粒子：2022年1月20日的广布太阳高能粒子事件
Solar energetic particles injected inside and outside a magnetic cloud: The widespread solar energetic particle event on 2022 January 20
AI总结：
本文研究2022年1月20日广布SEP事件，揭示粒子由CME驱动激波加速并注入先前存在的磁云内外，其中太阳轨道器观测到的向日传播粒子源于沿磁云西侧长腿注入，且磁云内电子传播路径比模型估计长约30%。
摘要：
背景。2022年1月20日，太阳轨道器（Solar Orbiter）上的高能粒子探测器（EPD）测量到一次太阳高能粒子（SEP）事件，显示出异常的首批粒子来自背日方向。与太阳轨道器在经度上向西相隔17°的近地航天器测量到经典的背日方向通量。与太阳轨道器分别向东相隔18°和向西相隔143°的STEREO-A和MAVEN也观测到该事件，表明粒子在日球层中至少扩散了160°。结果。太阳轨道器当时嵌入在一个于1月16日从同一活动区爆发的磁云（MC）中，该活动区与1月20日的SEP事件相关。该SEP事件与一次M5.5级耀斑和一个速度为1433 km/s的快速CME驱动激波有关，该激波在磁云内部和外部均注入了粒子。综合来看，较硬的SEP能谱、II型射电暴的存在，以及从80 MHz开始观测到的似乎源自II型射电暴的共时III型射电暴，表明该激波很可能是粒子的主要加速器。结论。我们对这次SEP事件的详细分析强烈表明，高能粒子主要由CME驱动的激波加速，并在粒子起始时刻注入到日球层中先前存在的磁云内部和外部。太阳轨道器测量到的向日传播的SEP是由粒子沿磁云仍与太阳相连的较长（西侧）腿注入而产生的。确定的磁云内部电子传播路径长度比基于渐变圆柱壳模型估计的磁云环腿长度长约30%，这与较低的场线旋转次数一致。
英文摘要：
Context. On 2022 January 20, the Energetic Particle Detector (EPD) on board Solar Orbiter measured a solar energetic particle (SEP) event showing unusual first arriving particles from the anti-Sun direction. Near-Earth spacecraft separated 17° in longitude to the west from Solar Orbiter measured classic antisunward-directed fluxes. STEREO-A and MAVEN, separated 18° to the east and 143° to the west from Solar Orbiter respectively, also observed the event, suggesting that particles spread over at least 160° in the heliosphere. Results. Solar Orbiter was embedded in a MC erupting on 16 January from the same active region as that related to the SEP event on 20 January. The SEP event is related to a M5.5 flare and a fast CME-driven shock of 1433 km/s, which injected particles within and outside the MC. Taken together, the hard SEP spectra, the presence of a Type II radio burst, and the co-temporal Type III radio burst being observed from 80 MHz that appears to emanate from the Type II burst, suggest that the shock is likely the main accelerator of the particles. Conclusions. Our detailed analysis of the SEP event strongly suggests that the energetic particles are mainly accelerated by a CME-driven shock and are injected into and outside of a previous MC present in the heliosphere at the time of the particle onset. The sunward-propagating SEPs measured by Solar Orbiter are produced by the injection of particles along the longer (western) leg of the MC still connected to the Sun at the time of the release of the particles. The determined electron propagation path length inside the MC is around 30% longer than the estimated length of the loop leg of the MC itself (based on the graduated cylindrical shell model), which is consistent with the low number of field line rotations.
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