A statistical evaluation of ballistic backmapping for the slow solar wind: The interplay of solar wind acceleration and corotation
A statistical evaluation of ballistic backmapping for the slow solar wind: The interplay of solar wind acceleration and corotation
复制标题
慢速太阳风弹道反向映射的统计评估：太阳风加速和共转的相互作用
DOI：
10.1093/mnras/stab2965
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发表时间：
2021
影响因子：
4.8
通讯作者：
S. Matt
中科院分区：
文献类型：
--
作者：
A. Macneil;M. Owens;Adam J. Finley;S. Matt
将太阳风等离子体映射回其源通常使用“两步弹道反映射”方法来实现。太阳风观测映射通过日光层的PFSS模式的边缘，通过假设一个恒定的速度，径向，等离子体湍流。通过模型追踪场线给出了1R处的源位置（cid：2）日光层映射组件取决于两个已知的误差源（来自太阳风加速和非径向湍流）有效抵消的论点。这一假设尚未经过统计检验。在这项研究中，我们评估了日光层部分的两步反映射，除了映射使用模型与明确的径向加速度，和方位角速度，v φ，来自角动量守恒。我们估计了地球观测到的326个日光层电流片（HCS）交叉点与2处相应交叉点之间的纵向映射偏移量（cid：3）φ。5来自PFSS模型的R（cid：2）。虽然详细的太阳风模型可以被优化以产生与HCS交叉数据具有良好平均一致性的（cid：3）φ，但弹道映射几乎表现得同样好，尽管所有残差具有相当大的标准偏差σ 16。我们的结论是，建议的误差消除可能有助于弹道映射的良好性能。然而，行星际加速度和有效太阳风共转的高度都比以前假设的要小。我们的结果进一步表明，早期帕克太阳探测器观测到的36 R（cid：2）左右的大v φ并不代表整个太阳风，因为它需要通过增加加速度来平衡。
Mapping solar wind plasma back to its source is often achieved using the ‘two-step ballistic backmapping’ method. Solar wind observations are mapped through the heliosphere to the edge of a PFSS model, by assuming a constant speed, radial, plasma flow. Tracing field lines through the model gives the source location at 1 R (cid:2) The heliospheric mapping component hinges upon the argument that two known sources of error, stemming from solar wind acceleration and non-radial flow, effectively cancel. This assumption has not been tested statistically. In this study, we evaluate the heliospheric portion of two-step backmapping, in addition to mapping using models with explicit radial acceleration, and azimuthal velocity, v φ , derived from angular momentum conservation. We estimate longitudinal mapping offsets, (cid:3)φ , between 326 Earth-observed crossings of the heliospheric current sheet (HCS), and corresponding crossings at 2 . 5 R (cid:2) from PFSS models. While the detailed solar wind models can be optimized to produce (cid:3)φ in good average agreement with HCS crossing data, the ballistic mapping performs almost as well, although all residuals have a sizeable standard deviation σ ∼ 16 ◦ . We conclude that the proposed error cancellation likely contributes to the good performance of ballistic mapping. However, interplanetary acceleration and the height of effective solar wind corotation are both smaller than previously assumed. Our results further suggest that early Parker Solar Probe observations of large v φ around 36 R (cid:2) do not represent the overall solar wind, due to the requirement for it to be balanced by increased acceleration.