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Analyzing the interstellar neutral He bulk flow parameters with IBEX-Lo.

机译：使用IBEX-Lo分析星际中性He整体流量参数。

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摘要

Our Sun is immersed in a local galactic environment which is composed of a warm, dilute, and partially ionized gas. Due to the Sun's motion relative to this environment, the interstellar neutral (ISN) gas flows through the heliosphere providing the opportunity to perform in-situ observations of the ISN gas from Earth's orbit. The Interstellar Boundary Explorer (IBEX) has observed the ISN gas flow over the past 7 years from a highly elliptical orbit around the Earth. The first observations of ISN H, O, and Ne were recorded by IBEX, along with the most detailed observation of ISN He. Since He is minimally influenced by ionization and charge exchange, the ISN He flow provides a sample of the pristine interstellar environment. Surprisingly, the analysis of the early IBEX observations of the ISN He flow in 2009 and 2010 with two separate analysis techniques indicated a somewhat different ISN He parameter set than the previous neutral gas observations with Ulysses GAS. One analysis technique employs the Warsaw Test Particle Model (WTPM) to simulate the ISN atom trajectories numerically from the observer position to the boundary of the heliosphere at 150 AU with spatial and temporal dependent ionization rates. A computational intensive global chi-squared minimization of the WTPM to IBEX-Lo observations is performed to characterize the ISN He flow. The second analysis technique, and the subject of this study, takes advantage of simplifications possible due to the IBEX viewing geometry of ISN atoms close to perihelion in their hyperbolic trajectories. The analytical model is based on Liouville's Theorem with the assumption that the ISN He distribution is a drifting Maxwellian in the local interstellar medium. The analytical model is used to make a 3-step approach to determining the ISN He flow vector and temperature, rather than a global chi-squared minimization. The first step determines the location of the peak ISN He flux at Earth orbit to fix the relationship between the ISN He flow speed and the ecliptic longitude flow direction at infinity. The second step observes the ISN He latitude distribution peak as a function of observer position at Earth orbit to determine the ISN He flow ecliptic longitude and latitude at infinity. The third step uses the observed ISN He flow latitude width to determine the ISN He temperature. Each step is performed independently, rather than a global chi-squared minimization, which helps separate the influence of other particle populations. Using the first 6 years of IBEX observations along with an improved understanding of secondary particle populations and varying the IBEX observation strategy, we have refined the derived ISN He flow parameters. The new parameter set becomes more similar to the past results from the Ulysses observations but with the added consequence of a much higher temperature: velocity 27.0 + 1.4(-1.3) km s-1, longitude 74.5° +/- 1.7°, latitude -5.2° +/- 0.3°, and temperature 8710 + 540(-740) K.
机译：我们的太阳浸入由温暖，稀薄和部分离子化的气体组成的局部银河环境中。由于太阳相对于此环境的运动，星际中性（ISN）气体流经日光层，为从地球轨道对ISN气体进行原位观测提供了机会。星际边界探测器（IBEX）在过去7年中观察到了ISN气体从环绕地球的高度椭圆轨道流动的情况。 IBEX记录了ISN H，O和Ne的最初观测结果，以及ISN He的最详细观测结果。由于He受电离和电荷交换的影响极小，因此ISN He流量提供了原始星际环境的样本。出乎意料的是，使用两种单独的分析技术对ISN He流量在2009年和2010年的IBEX早期观测进行的分析表明，与先前使用Ulysses GAS进行的中性气体观测相比，ISN He参数集有所不同。一种分析技术采用华沙测试粒子模型（WTPM），以空间和时间相关的电离速率，以150 AU数值模拟ISN原子轨迹，从观察者位置到日球边界。对WTPM到IBEX-Lo观测值进行计算密集的全局卡方最小化，以表征ISN He流量。第二种分析技术以及本研究的主题利用了可能的简化，这是因为ISN原子在其双曲线轨迹中接近近日点的IBEX观察几何形状。该分析模型基于Liouville定理，并假设ISN He分布是本地星际介质中的漂移Maxwellian。该分析模型用于确定ISN He流量矢量和温度的三步法，而不是全局卡方最小化。第一步，确定ISN He峰值通量在地球轨道上的位置，以固定ISN He流速与黄道经度无限远方向之间的关系。第二步观察ISN He纬度分布峰随观测者在地球轨道位置的变化，以确定ISN He流量黄道经度和无限远处的纬度。第三步使用观测到的ISN He流量纬度宽度确定ISN He温度。每个步骤都是独立执行的，而不是全局卡方最小化，这有助于分离其他粒子群体的影响。使用IBEX观测的前6年，以及对次级粒子种群的更好理解并改变IBEX观测策略，我们对导出的ISN He流量参数进行了改进。新的参数集与Ulysses观测的过去结果更加相似，但具有更高的温度附加结果：速度27.0 + 1.4（-1.3）km s-1，经度74.5°+/- 1.7°，纬度- 5.2°+/- 0.3°，温度8710 + 540（-740）K。

著录项

  • 作者

    Leonard, Trevor W.;

  • 作者单位

    University of New Hampshire.;

  • 授予单位 University of New Hampshire.;
  • 学科 Astrophysics.
  • 学位 Ph.D.
  • 年度 2016
  • 页码 75 p.
  • 总页数 75
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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