标题： 基于STEREO-A或STEREO-B日球成像仪观测的ELEvoHI CME到达预测为何不同？ 显示英文标题

标题： Why are ELEvoHI CME arrival predictions different if based on STEREO-A or STEREO-B heliospheric imager observations?

摘要： 准确预测日冕物质抛射（CMEs）到达时间和到达速度是空间天气研究中的一个未解问题。 在本研究中，基于两个STEREO优势点的输入，独立地对每个CME的预测到达时间和速度进行了比较。 我们使用基于日球成像仪观测（ELEvoHI）集合建模的ELlipse Evolution模型进行回溯预测。 通过Wang-Sheeley-Arge/日球上游外推（WSA/HUX）模型组合获得环境太阳风条件的估计值，该值作为ELEvoHI的输入。 我们仔细选择了2010年2月至2012年7月之间的12个CME，这些CME在STEREO-A和STEREO-B HI时间-延伸图中显示出清晰的特征，沿着黄道面附近传播，并且在地球上有相应的原位特征。 我们发现来自两个不同视角的预测到达时间平均差异为6.5小时，对于个别CME可达到9.5小时，而平均到达速度差异为63 km s$^{-1}$。 环境太阳风速度变化较大会导致STEREO-A和STEREO-B CME到达时间预测差异更大（$cc~=~0.92$）。 此外，我们将两个航天器的预测到达情况与地球上的实际原位到达情况进行比较，发现到达时间的平均绝对误差为7.5$\pm$9.5小时，到达速度的平均绝对误差为87$\pm$111 km s$^{-1}$。 没有迹象表明其中一个航天器提供的到达预测比另一个更准确。 显示英文摘要

摘要： Accurate forecasting of the arrival time and arrival speed of coronal mass ejections (CMEs) is a unsolved problem in space weather research. In this study, a comparison of the predicted arrival times and speeds for each CME based, independently, on the inputs from the two STEREO vantage points is carried out. We perform hindcasts using ELlipse Evolution model based on Heliospheric Imager observations (ELEvoHI) ensemble modelling. An estimate of the ambient solar wind conditions is obtained by the Wang-Sheeley-Arge/Heliospheric Upwind eXtrapolation (WSA/HUX) model combination that serves as input to ELEvoHI. We carefully select 12 CMEs between February 2010 and July 2012 that show clear signatures in both STEREO-A and STEREO-B HI time-elongation maps, that propagate close to the ecliptic plane, and that have corresponding in situ signatures at Earth. We find a mean arrival time difference of 6.5 hrs between predictions from the two different viewpoints, which can reach up to 9.5 hrs for individual CMEs, while the mean arrival speed difference is 63 km s$^{-1}$. An ambient solar wind with a large speed variance leads to larger differences in the STEREO-A and STEREO-B CME arrival time predictions ($cc~=~0.92$). Additionally, we compare the predicted arrivals, from both spacecraft, to the actual in situ arrivals at Earth and find a mean absolute error of 7.5 $\pm$ 9.5 hrs for the arrival time and 87 $\pm$ 111 km s$^{-1}$ for the arrival speed. There is no tendency for one spacecraft to provide more accurate arrival predictions than the other.