根据费米/LAT对> 100条MeV γ射线的观测推断太阳粒子加速和输运
Particle Acceleration and Transport at the Sun Inferred from Fermi/LAT Observations of >100 MeV Gamma-rays
摘要：
来自太阳的持续伽马射线发射（SGRE）事件与超快（2000 km/s或更高）晕日冕物质抛射（CME）和十米-百米（DH）波长的II型射电爆发有关。SGRE持续时间与II型爆发持续时间线性相关，表明SGRE所需的> 300 MeV质子被加速产生II型爆发的数十keV电子的相同冲击加速。当磁连接良好时，相关的太阳高能粒子（SEP）事件具有硬谱，表明高能质子的大量加速。在Fermi/LAT于2014年1月7日观测到的SGRE事件中，GOES探测到的SEP事件具有非常软的光谱，没有太多超过100 MeV的粒子。这与SGRE的存在相矛盾，意味着存在大量> 300 MeV的质子。此外，II型爆发和SGRE的持续时间与它们之间的已知线性关系一致（Gopalswamy等人，2018，ApJ 868，L19）。我们表明，软频谱是由于不良的磁连接的冲击鼻地球观测。尽管爆发的位置（S15W11）靠近盘中心，但CME的传播是非径向的，使CME的侧面穿过黄道而不是鼻子。高能粒子在机头附近被加速，因此它们不会到达GOES，但它们会沉淀到喷发区域附近，产生SGRE。这项研究提供了进一步的证据，SGRE是由质子加速冲击和传播向太阳与大气离子相互作用。
英文摘要：
The sustained gamma-ray emission (SGRE) events from the Sun are associated with an ultrafast (2000 km/s or greater) halo coronal mass ejection (CME) and a type II radio burst in the decameter-hectometric (DH) wavelengths. The SGRE duration is linearly related to the type II burst duration indicating that >300 MeV protons required for SGREs are accelerated by the same shock that accelerates tens of keV electrons that produce type II bursts. When magnetically well connected, the associated solar energetic particle (SEP) event has a hard spectrum, indicating copious acceleration of high-energy protons. In one of the SGRE events observed on 2014 January 7 by Fermi/LAT, the SEP event detected by GOES has a very soft spectrum with not many particles beyond 100 MeV. This contradicts the presence of the SGRE, implying the presence of significant number of >300 MeV protons. Furthermore, the durations of the type II burst and the SGRE agree with the known linear relationship between them (Gopalswamy et al. 2018, ApJ 868, L19). We show that the soft spectrum is due to poor magnetic connectivity of the shock nose to an Earth observer. Even though the location of the eruption (S15W11) is close to the disk center, the CME propagated non-radially making the CME flank crossing the ecliptic rather than the nose. High-energy particles are accelerated near the nose, so they do not reach GOES but they do precipitate to the vicinity of the eruption region to produce SGRE. This study provides further evidence that SGRE is caused by protons accelerated in shocks and propagating sunward to interact with the atmospheric ions.
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