Lyα Absorption from Heliosheath Neutrals
Lyα Absorption from Heliosheath Neutrals
复制标题
日鞘中性粒子对 Lyα 的吸收
DOI：
10.1086/510844
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发表时间：
2006
期刊：
影响因子：
--
通讯作者：
Y. Malama
中科院分区：
文献类型：
--
作者：
B. Wood;V. Izmodenov;J. Linsky;Y. Malama
我们评估了恒星 Lyα 线的 HST 观测可以提供的关于日鞘（终止激波和日球层顶之间的日光层区域）的信息。为了寻找日鞘吸收的证据，我们对校正 ISM 吸收（以及日光层/天文层吸收，如果存在）后重建的恒星 Lyα 线进行了系统检查。正如预期的那样，大多数恒星线都很好地集中在恒星径向速度上，但相对于 ISM 流具有最大顺风方向的三个视线（χ1 Ori、HD 28205 和 HD 28568）具有明显蓝移的 Lyα 线。由于在顺风方向，日鞘吸收最强，因此蓝移几乎肯定是由之前未检测到的日鞘吸收引起的。我们对日鞘吸收和一对日光层模型的预测进行了初步比较。在日光层内对等离子体进行复杂的多组分处理的模型预测吸收率比采用简单的单流体处理的模型要少，这使得与数据的一致性更好。最后，我们发现火星快车上的 ASPERA-3 仪器测量到的非行星高能中性原子 (ENA) 通量（被解释为来自日鞘）可能太高，无法与 HST 观测到的日鞘吸收相对缺乏的情况相一致。这表明这些 ENA 的本地行星际源而不是日鞘源。
We assess the information that HST observations of stellar Lyα lines can provide on the heliosheath, the region of the heliosphere between the termination shock and heliopause. To search for evidence of heliosheath absorption, we conduct a systematic inspection of stellar Lyα lines reconstructed after correcting for ISM absorption (and heliospheric/astrospheric absorption, if present). Most of the stellar lines are well centered on the stellar radial velocity, as expected, but the three lines of sight with the most downwind orientations relative to the ISM flow (χ1 Ori, HD 28205, and HD 28568) have significantly blueshifted Lyα lines. Since it is in downwind directions that heliosheath absorption should be strongest, the blueshifts are almost certainly caused by previously undetected heliosheath absorption. We make an initial comparison between the heliosheath absorption and the predictions of a pair of heliospheric models. A model with a complex multicomponent treatment of plasma within the heliosphere predicts less absorption than a model with a simple single-fluid treatment, which leads to better agreement with the data. Finally, we find that nonplanetary energetic neutral atom (ENA) fluxes measured by the ASPERA-3 instrument on board Mars Express, which have been interpreted as being from the heliosheath, are probably too high to be consistent with the relative lack of heliosheath absorption seen by HST. This would argue for a local interplanetary source for these ENAs instead of a heliosheath source.