Detectability of neutral interstellar deuterium by a forthcoming SMEX mission IBEX
Detectability of neutral interstellar deuterium by a forthcoming SMEX mission IBEX
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即将到来的 SMEX 任务 IBEX 可探测到中性星际氘
DOI：
10.1051/0004-6361:200809593
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发表时间：
2008
期刊：
影响因子：
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通讯作者：
M. Bzowski
中科院分区：
文献类型：
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作者：
S. Tarnopolski;M. Bzowski
语境。我们研究了即将到来的 NASA SMEX 任务 IBEX 探测中性星际氘的可行性。目标。通过数值模拟，我们研究了中性星际氘在地球轨道上的绝对密度和通量，并使用 IBEX 检查了其可探测性。方法。我们的模拟是使用华沙 3D 内日球层中性星际气体的时间相关测试粒子模型（特别适合氘的情况）以及最先进的电离场和辐射压力模型进行的。该模型预测了太阳周期期间地球不同位置的星际 D 的密度、体积速度和通量。我们特别注意进行 IBEX 观测的时间间隔。结果。通过我们的模拟，我们预测地球轨道中的氘丰度相对于终止激波处的丰度将大幅增加。除每年 9 月至 11 月之间的短暂时间间隔外，IBEX 的 D 原子能量将位于其 Lo 仪器的能量敏感带内。由于IBEX特殊的观测几何结构，每年都会有一次搜索I/S D的机会，即地球接近黄道经度$165\degr$时，即三月份。假设 D 的 TS 丰度与本地云中相同，等于 $1.56 \times 10^{-5}$，并且 TS 处 H 的密度为 0.11 cm -2 s -1 ，我们估计预期相对通量约为 0.015 cm -2 s -1 ，对应于约 0.007 cm -2 s -1 的局部绝对通量。预期通量对太阳周期相位的依赖性相对较弱。通量与终止激波处的氘密度成正比，并且仅微弱地依赖于该区域中气体的体积速度和温度。
Context. We study the feasibility of detection of neutral interstellar deuterium by the forthcoming NASA SMEX mission IBEX. Aims. Using numerical simulations, we study the absolute density and flux in Earth orbit of neutral interstellar deuterium and check its detectability using IBEX. Methods. Our simulations were performed using the Warsaw 3D time-dependent test-particle model of neutral interstellar gas in the inner heliosphere, which was specially adapted to the case of deuterium, and state-of-the-art models of the ionization field and radiation pressure. The modeling predicted the density, bulk velocity, and flux of interstellar D at different positions of the Earth during the solar cycle. We paid particular attention to the time interval in which IBEX observations will be performed. Results. Using our simulations, we predict a large enhancement of deuterium abundance in Earth orbit with respect to the abundance at the termination shock. The energy of the D atoms at IBEX will be within the energetic sensitivity band of its Lo instrument, apart from during a short time interval between September and November each year. Because of the specific observing geometry of IBEX, there will be one opportunity each year to search for I/S D, when Earth is close to ecliptic longitude $165\degr$, i.e. in March. Assuming that the TS abundance of D is identical as in the Local Cloud, which is equal to $1.56 \times 10^{-5}$, and that the density of H at TS is 0.11 cm -2 s -1 , we estimate the expected relative flux to be approximately 0.015 cm -2 s -1 , which corresponds to the local absolute flux of about 0.007 cm -2 s -1 . The dependence of the expected flux on the phase of solar cycle is relatively weak. The flux scales proportionally to the density of deuterium at the termination shock and depends only weakly on the bulk velocity and temperature of the gas in this region.