The Magnetic Field Environment of Active Region 12673 That Produced the Energetic Particle Events of September 2017
The Magnetic Field Environment of Active Region 12673 That Produced the Energetic Particle Events of September 2017
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DOI：
10.3847/1538-4357/ac8d69
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发表时间：
2022-08
期刊：
影响因子：
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通讯作者：
S. Yardley;L. Green;A. James;D. Stansby;T. Mihailescu
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作者：
S. Yardley;L. Green;A. James;D. Stansby;T. Mihailescu
预测太阳高能粒子（SEP），并识别耀斑/日冕物质抛射（CME）的活动区（AR），将提前产生SEP事件是极具挑战性的。我们调查了AR 12673的磁场环境，包括AR的磁场配置，在AR附近的周围场配置，衰减指数分布，和地球连接的磁场的足迹，在四个爆发事件的时间。其中两个爆发事件是SEP生产（2017年9月4日20：00 UT和9月6日11：56 UT），而两个不是（9月4日18：05 UT和9月7日14：33 UT）。我们分析了一系列EUV和白光日冕观测沿着与位场外推，发现与SEP生产事件相关的CME要么触发零点重联，将耀斑加速粒子从耀斑站点重定向到地球连接的领域和/或有一个显着的扩展（和冲击形成）到开放的地球连接的领域。衰变指数随高度的变化率表明，该区域可能会产生快速的日冕物质抛射（v > 1500 km s−1），这在事件2和事件3中确实发生了。AR的磁场环境，包括开放磁场和零点的位置沿着CME的磁场连通性和传播方向，在SEP逃逸和到达地球方面起着重要作用。应调查其他产生SEP的AR，以确定它们的磁场环境和CME传播方向是否对SEP逃逸和到达地球有重要影响。
Forecasting solar energetic particles (SEPs), and identifying flares/coronal mass ejections (CMEs) from active regions (ARs) that will produce SEP events in advance is extremely challenging. We investigate the magnetic field environment of AR 12673, including the AR’s magnetic configuration, the surrounding field configuration in the vicinity of the AR, the decay index profile, and the footpoints of the Earth-connected magnetic field, around the time of four eruptive events. Two of the eruptive events are SEP productive (2017 September 4 at 20:00 UT and September 6 at 11:56 UT), while two are not (September 4 at 18:05 UT and September 7 at 14:33 UT). We analyzed a range of EUV and white-light coronagraph observations along with potential field extrapolations and find that the CMEs associated with the SEP-productive events either trigger null point reconnection that redirects flare-accelerated particles from the flare site to the Earth-connected field and/or have a significant expansion (and shock formation) into the open Earth-connected field. The rate of change of the decay index with height indicates that the region could produce a fast CME (v > 1500 km s−1), which it did during events 2 and 3. The AR’s magnetic field environment, including locations of open magnetic field and null points along with the magnetic field connectivity and propagation direction of the CMEs play an important role in the escape and arrival of SEPs at Earth. Other SEP-productive ARs should be investigated to determine whether their magnetic field environment and CME propagation direction are significant in the escape and arrival of SEPs at Earth.