Imprint of the Sun’s Evolving Polar Winds on IBEX Energetic Neutral Atom All-sky Observations of the Heliosphere
Imprint of the Sun’s Evolving Polar Winds on IBEX Energetic Neutral Atom All-sky Observations of the Heliosphere
复制标题
太阳演化的极地风对 IBEX 高能中性原子日光层全天观测的影响
DOI：
10.3847/1538-4357/aa850b
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
J. Sokół
中科院分区：
文献类型：
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作者：
E. Zirnstein;M. Dayeh;D. McComas;J. Sokół
通过7年的星际边界探测器（IBEX）对高能中性原子（ENA）的测量，IBEX显示了太阳风动态变化与日光层对ENA形成的响应之间的明显相关性。在本文中，我们调查的随纬度变化的ENA光谱从IBEX和它们的关系，在1 Au观测到的太阳风速度的时间变化。我们发现，ENA谱指数在低（1.8）和高（1.8）值之间的过渡的纬度的变化，以及在高纬度和低纬度的ENA谱指数的分布，以及与1 Au附近观测到的快，慢太阳风纬度结构的演变相关。这种相关性包括由于太阳风传播到终端激波并进入内日鞘所需的时间，以及ENA通过电荷交换产生并向1 Au返回所需的时间。此外，我们观察到的ENA光谱在北方和南半球的陡峭的时间不对称性，在太阳风和极地冕洞观察到的不对称性一致。虽然这种不对称性是在日球层的逆风方向附近观察到的，但在尾部方向还没有观察到，这表明视线积分距离较长，或者终端激波下游的太阳风等离子体处理不同。
With 7 years of Interstellar Boundary Explorer (IBEX) measurements of energetic neutral atoms (ENAs), IBEX has shown a clear correlation between dynamic changes in the solar wind and the heliosphere’s response in the formation of ENAs. In this paper, we investigate temporal variations in the latitudinal-dependent ENA spectrum from IBEX and their relationship to the solar wind speed observed at 1 au. We find that the variation in latitude of the transition in ENA spectral indices between low (≲1.8) and high (≳1.8) values, as well as the distribution of ENA spectral indices at high and low latitudes, correlates well with the evolution of the fast and slow solar wind latitudinal structure observed near 1 au. This correlation includes a delay due to the time it takes the solar wind to propagate to the termination shock and into the inner heliosheath, and for ENAs to be generated via charge-exchange and travel back toward 1 au. Moreover, we observe a temporal asymmetry in the steepening of the ENA spectrum in the northern and southern hemispheres, consistent with asymmetries observed in the solar wind and polar coronal holes. While this asymmetry is observed near the upwind direction of the heliosphere, it is not yet observed in the tail direction, suggesting a longer line-of-sight integration distance or different processing of the solar wind plasma downstream of the termination shock.