Evidence of direct detection of interstellar deuterium in the local interstellar medium by IBEX
Evidence of direct detection of interstellar deuterium in the local interstellar medium by IBEX
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IBEX直接探测局部星际介质中星际氘的证据
DOI：
10.1051/0004-6361/201321420
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发表时间：
2013
影响因子：
6.5
通讯作者：
N. Schwadron
中科院分区：
文献类型：
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作者：
D. F. Moreno;P. Wurz;L. Saul;M. Bzowski;M. Kubiak;J. Sokół;P. Frisch;S. Fuselier;D. McComas;E. Möbius;N. Schwadron
我们报告的第一个原位测量中性氘起源于本地星际介质（LISM）在地球轨道上。这些测量是用NASA星际边界探测器（IBEX）卫星上的IBEX-Lo相机进行的。分析了2009年至2011年春季观测期间的所有数据。在IBEX三年的使命时间内，观测几何和轨道允许LISM的总观测时间为115.3天。然而，旋转的航天器和通过8个能量通道的影响意味着我们只观察了1.44天的星际风，其中收集了2个星际氘计数。我们在这里报告了一个保守的数字，因为系统误差或额外噪声的可能性，虽然在我们的分析中消除了我们所知的最好的，只支持在1西格玛水平的检测。从这些观测结果中，我们得出在1 Au处D/H的比值为5.8 ± 4.4 × 10 −4。在模拟了D和H从终止激波到地球轨道的输运和损失之后，我们发现我们的结果D/HLISM = 1.6 ± 1.2 × 10 −5与本地星际云的D/HLIC = 1.6 ± 0.4 × 10 −5一致。这种微弱的星际信号是从强烈的地球背景信号中提取的，该背景信号由传感器转换表面的溅射产物组成。作为参考，我们准确地测量了这些溅射产物中的陆地D/H比，然后区分这种陆地背景源。由于减少D和H信号在地球轨道上的太阳活动上升期间，由于光电离损失和增加的光子压力，我们的研究结果表明，在原位测量星际氘在内日光层是唯一可能的太阳能最低条件。
We report the first in situ measurements of neutral deuterium originating in the local interstellar medium (LISM) in Earth’s orbit. These measurements were performed with the IBEX-Lo camera on NASA’s interstellar boundary explorer (IBEX) satellite. All data from the spring observation periods of 2009 through 2011 have been analysed. In the three years of the IBEX mission time, the observation geometry and orbit allowed for a total observation time of 115.3 days for the LISM. However, the effects of the spinning spacecraft and the stepping through 8 energy channels mean that we are only observing the interstellar wind for a total time of 1.44 days, in which 2 counts for interstellar deuterium were collected. We report here a conservative number, because a possibility of systematic error or additional noise, though eliminated in our analysis to the best of our knowledge, only supports detection at a 1-sigma level. From these observations, we derive a ratio D/H = � 5.8 ± 4.4 � × 10 −4 at 1 AU. After modelling the transport and loss of D and H from the termination shock to Earth’s orbit, we find that our result of D/HLISM = � 1.6 ± 1.2 � × 10 −5 agrees with D/HLIC = � 1.6 ± 0.4 � × 10 −5 for the local interstellar cloud. This weak interstellar signal is extracted from a strong terrestrial background signal consisting of sputter products from the sensor’s conversion surface. As reference, we accurately measure the terrestrial D/H ratio in these sputtered products and then discriminate this terrestrial background source. Because of the diminishing D and H signal at Earth’s orbit during the rising solar activity due to photoionisation losses and increased photon pressure, our result demonstrates that in situ measurements of interstellar deuterium in the inner heliosphere are only possible during solar minimum conditions.